Requesting operations for an account sometimes returns a different amount of results for the same request

When calling `https://mainnet.blockchainos.org/api/v1/accounts/GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR/operations?cursor=JEdBN0FCQkNTTEY2T1BLNkJPTjQzQ1NWVzZINVdNWFpFS0lKNDM3Mk9QM1I0M0VEUFRQMjVJR09SLQAAAAAABgnJAAAAAAAAAAA3MDNjNTYxMC0wNDIyLTExZTktYjFlYi0wMjQyYWMxMjAwMDI%3D&limit=20&reverse=true`, _embedded.records sometimes contain a different amount of records.

The bug can be reproduced, but the behavior is inconsistent. I had to perform the request multiple times to get the different responses below.

I'm not sure if this is a bug related to the operations for an account endpoint, or if it relates to all other endpoints as well.

Call 1 (the desired response) containing 4 records
``` json
{
"_embedded": {
"records": [
{
"_links": {
"self": {
"href": "/api/v1/transactions/B2LPnAkctZVsrPVazgAn2SuM8WDy84pk1ReEVkopGGkZ/operations/223"
},
"transaction": {
"href": "/api/v1/transactions/B2LPnAkctZVsrPVazgAn2SuM8WDy84pk1ReEVkopGGkZ"
}
},
"block_height": 348545,
"body": {
"target": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"amount": "27976564374"
},
"confirmed": "2018-12-17T13:10:33.279197406Z",
"hash": "5nunt3dhp3Fodv9Ppk6nSqcNGJtVJimoji7DaWnz16Nq-B2LPnAkctZVsrPVazgAn2SuM8WDy84pk1ReEVkopGGkZ",
"index": 223,
"proposed_time": "2018-12-17T13:10:33.265373938Z",
"source": "GCD2K7NFW6IBLSLYX5IZMYVVN2ETASI674Q4V4VAPHBIHRXXBTUWKTXT",
"target": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"tx_hash": "B2LPnAkctZVsrPVazgAn2SuM8WDy84pk1ReEVkopGGkZ",
"type": "payment"
},
{
"_links": {
"self": {
"href": "/api/v1/transactions/Edaup5W5DK1catNcgFwTwyDFZDiNtq6nuQwmzSdqTXiF/operations/0"
},
"transaction": {
"href": "/api/v1/transactions/Edaup5W5DK1catNcgFwTwyDFZDiNtq6nuQwmzSdqTXiF"
}
},
"block_height": 35604,
"body": {
"target": "GCAP52WC7SJZXPNWCSSBJVD55PE2VBHBPQOW3PAOAJNIEXKYZFPLHTOO",
"amount": "229180000000"
},
"confirmed": "2018-11-29T09:44:25.759358708Z",
"hash": "GWUKgUP99afpYfA18w9VCTNY4PQmbqAULBD3VDheWwFb-Edaup5W5DK1catNcgFwTwyDFZDiNtq6nuQwmzSdqTXiF",
"index": 0,
"proposed_time": "2018-11-29T09:25:12.950735722Z",
"source": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"target": "GCAP52WC7SJZXPNWCSSBJVD55PE2VBHBPQOW3PAOAJNIEXKYZFPLHTOO",
"tx_hash": "Edaup5W5DK1catNcgFwTwyDFZDiNtq6nuQwmzSdqTXiF",
"type": "payment"
},
{
"_links": {
"self": {
"href": "/api/v1/transactions/3cx4G5L8h6p8eAAbcbtY7SDCmQ8PA6WWbfs9hWG8er7E/operations/0"
},
"transaction": {
"href": "/api/v1/transactions/3cx4G5L8h6p8eAAbcbtY7SDCmQ8PA6WWbfs9hWG8er7E"
}
},
"block_height": 35357,
"body": {
"target": "GAFCGKMUQ34ZDD3I2NS2RFBOGIQEUUHREH5WRPCGBSOWYUUJJUEWPRMO",
"amount": "1400000000000",
"linked": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR"
},
"confirmed": "2018-11-29T09:43:55.418548352Z",
"hash": "Ho5aGJURVpj8USEGDgj2GJjcQEYc1JGZdqdAmi9m2Vht-3cx4G5L8h6p8eAAbcbtY7SDCmQ8PA6WWbfs9hWG8er7E",
"index": 0,
"proposed_time": "2018-11-29T08:59:37.764130154Z",
"source": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"target": "GAFCGKMUQ34ZDD3I2NS2RFBOGIQEUUHREH5WRPCGBSOWYUUJJUEWPRMO",
"tx_hash": "3cx4G5L8h6p8eAAbcbtY7SDCmQ8PA6WWbfs9hWG8er7E",
"type": "create-account"
},
{
"_links": {
"self": {
"href": "/api/v1/transactions/CvbUf2gNzJZFsKkkFbwHQsuVv97aKd8jpGTf7iCgjKi8/operations/798"
},
"transaction": {
"href": "/api/v1/transactions/CvbUf2gNzJZFsKkkFbwHQsuVv97aKd8jpGTf7iCgjKi8"
}
},
"block_height": 230,
"body": {
"target": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"amount": "1629189227504"
},
"confirmed": "2018-11-27T07:48:10.883635297Z",
"hash": "92fW1T9nVt9WKrr1Y6sDyLfH6SutFGedNCK3hqPzTVDM-CvbUf2gNzJZFsKkkFbwHQsuVv97aKd8jpGTf7iCgjKi8",
"index": 798,
"proposed_time": "2018-11-27T07:48:10.817828899Z",
"source": "GAMX6BVPNPWWRGGAUZGT57YG4ZYNI3FO5UHXYSGYBODQVFWIEBWVFDRX",
"target": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"tx_hash": "CvbUf2gNzJZFsKkkFbwHQsuVv97aKd8jpGTf7iCgjKi8",
"type": "create-account"
}
]
},
"_links": {
"next": {
"href": "/api/v1/accounts/GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR/operations?cursor=JEdBN0FCQkNTTEY2T1BLNkJPTjQzQ1NWVzZINVdNWFpFS0lKNDM3Mk9QM1I0M0VEUFRQMjVJR09SLQAAAAAABVGBAAAAAAAAAAAyMzc5OGNkYy0wMWZkLTExZTktYjFlYi0wMjQyYWMxMjAwMDI%3D&limit=20&reverse=false"
},
"prev": {
"href": "/api/v1/accounts/GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR/operations?cursor=JEdBN0FCQkNTTEY2T1BLNkJPTjQzQ1NWVzZINVdNWFpFS0lKNDM3Mk9QM1I0M0VEUFRQMjVJR09SLQAAAAAAAADmAAAAAAAAAAFjZDhhYjYzYy1mMjE4LTExZTgtODk0YS0wMjQyYWMxMjAwMDI%3D&limit=20&reverse=true"
},
"self": {
"href": "/api/v1/accounts/GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR/operations?cursor=JEdBN0FCQkNTTEY2T1BLNkJPTjQzQ1NWVzZINVdNWFpFS0lKNDM3Mk9QM1I0M0VEUFRQMjVJR09SLQAAAAAABgnJAAAAAAAAAAA3MDNjNTYxMC0wNDIyLTExZTktYjFlYi0wMjQyYWMxMjAwMDI%3D&limit=20&reverse=true"
}
}
}
```

Call 2 (the faulty response) containing 5 records
``` json
{
"_embedded": {
"records": [
{
"_links": {
"self": {
"href": "/api/v1/transactions/HL52XFujFJa6jDpMVeD5ZkFziGf52qjjtYmknXitpMXb/operations/542"
},
"transaction": {
"href": "/api/v1/transactions/HL52XFujFJa6jDpMVeD5ZkFziGf52qjjtYmknXitpMXb"
}
},
"block_height": 395721,
"body": {
"target": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"amount": "10000000000"
},
"confirmed": "2018-12-20T06:42:33.250196235Z",
"hash": "7t9DEpV2BczwAzVfhNafenAxqV4EL7abkkQLhwE2BDWi-HL52XFujFJa6jDpMVeD5ZkFziGf52qjjtYmknXitpMXb",
"index": 542,
"proposed_time": "2018-12-20T06:42:33.240223454Z",
"source": "GAKHZ2O6CUSYACJEPUIGDXH6I554QLIQV5QOX7EKPFOAVP7KNHUV2OW2",
"target": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"tx_hash": "HL52XFujFJa6jDpMVeD5ZkFziGf52qjjtYmknXitpMXb",
"type": "payment"
},
{
"_links": {
"self": {
"href": "/api/v1/transactions/B2LPnAkctZVsrPVazgAn2SuM8WDy84pk1ReEVkopGGkZ/operations/223"
},
"transaction": {
"href": "/api/v1/transactions/B2LPnAkctZVsrPVazgAn2SuM8WDy84pk1ReEVkopGGkZ"
}
},
"block_height": 348545,
"body": {
"target": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"amount": "27976564374"
},
"confirmed": "2018-12-17T13:10:33.272188506Z",
"hash": "5nunt3dhp3Fodv9Ppk6nSqcNGJtVJimoji7DaWnz16Nq-B2LPnAkctZVsrPVazgAn2SuM8WDy84pk1ReEVkopGGkZ",
"index": 223,
"proposed_time": "2018-12-17T13:10:33.265373938Z",
"source": "GCD2K7NFW6IBLSLYX5IZMYVVN2ETASI674Q4V4VAPHBIHRXXBTUWKTXT",
"target": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"tx_hash": "B2LPnAkctZVsrPVazgAn2SuM8WDy84pk1ReEVkopGGkZ",
"type": "payment"
},
{
"_links": {
"self": {
"href": "/api/v1/transactions/Edaup5W5DK1catNcgFwTwyDFZDiNtq6nuQwmzSdqTXiF/operations/0"
},
"transaction": {
"href": "/api/v1/transactions/Edaup5W5DK1catNcgFwTwyDFZDiNtq6nuQwmzSdqTXiF"
}
},
"block_height": 35604,
"body": {
"target": "GCAP52WC7SJZXPNWCSSBJVD55PE2VBHBPQOW3PAOAJNIEXKYZFPLHTOO",
"amount": "229180000000"
},
"confirmed": "2018-11-29T09:36:57.789949439Z",
"hash": "GWUKgUP99afpYfA18w9VCTNY4PQmbqAULBD3VDheWwFb-Edaup5W5DK1catNcgFwTwyDFZDiNtq6nuQwmzSdqTXiF",
"index": 0,
"proposed_time": "2018-11-29T09:25:12.950735722Z",
"source": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"target": "GCAP52WC7SJZXPNWCSSBJVD55PE2VBHBPQOW3PAOAJNIEXKYZFPLHTOO",
"tx_hash": "Edaup5W5DK1catNcgFwTwyDFZDiNtq6nuQwmzSdqTXiF",
"type": "payment"
},
{
"_links": {
"self": {
"href": "/api/v1/transactions/3cx4G5L8h6p8eAAbcbtY7SDCmQ8PA6WWbfs9hWG8er7E/operations/0"
},
"transaction": {
"href": "/api/v1/transactions/3cx4G5L8h6p8eAAbcbtY7SDCmQ8PA6WWbfs9hWG8er7E"
}
},
"block_height": 35357,
"body": {
"target": "GAFCGKMUQ34ZDD3I2NS2RFBOGIQEUUHREH5WRPCGBSOWYUUJJUEWPRMO",
"amount": "1400000000000",
"linked": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR"
},
"confirmed": "2018-11-29T09:36:27.516757818Z",
"hash": "Ho5aGJURVpj8USEGDgj2GJjcQEYc1JGZdqdAmi9m2Vht-3cx4G5L8h6p8eAAbcbtY7SDCmQ8PA6WWbfs9hWG8er7E",
"index": 0,
"proposed_time": "2018-11-29T08:59:37.764130154Z",
"source": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"target": "GAFCGKMUQ34ZDD3I2NS2RFBOGIQEUUHREH5WRPCGBSOWYUUJJUEWPRMO",
"tx_hash": "3cx4G5L8h6p8eAAbcbtY7SDCmQ8PA6WWbfs9hWG8er7E",
"type": "create-account"
},
{
"_links": {
"self": {
"href": "/api/v1/transactions/CvbUf2gNzJZFsKkkFbwHQsuVv97aKd8jpGTf7iCgjKi8/operations/798"
},
"transaction": {
"href": "/api/v1/transactions/CvbUf2gNzJZFsKkkFbwHQsuVv97aKd8jpGTf7iCgjKi8"
}
},
"block_height": 230,
"body": {
"target": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"amount": "1629189227504"
},
"confirmed": "2018-11-27T07:48:10.883635297Z",
"hash": "92fW1T9nVt9WKrr1Y6sDyLfH6SutFGedNCK3hqPzTVDM-CvbUf2gNzJZFsKkkFbwHQsuVv97aKd8jpGTf7iCgjKi8",
"index": 798,
"proposed_time": "2018-11-27T07:48:10.817828899Z",
"source": "GAMX6BVPNPWWRGGAUZGT57YG4ZYNI3FO5UHXYSGYBODQVFWIEBWVFDRX",
"target": "GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR",
"tx_hash": "CvbUf2gNzJZFsKkkFbwHQsuVv97aKd8jpGTf7iCgjKi8",
"type": "create-account"
}
]
},
"_links": {
"next": {
"href": "/api/v1/accounts/GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR/operations?cursor=JEdBN0FCQkNTTEY2T1BLNkJPTjQzQ1NWVzZINVdNWFpFS0lKNDM3Mk9QM1I0M0VEUFRQMjVJR09SLQAAAAAABgnJAAAAAAAAAAA3MDFmODg4NC0wNDIyLTExZTktOTNlZi0wMjQyYWMxMjAwMDI%3D&limit=20&reverse=false"
},
"prev": {
"href": "/api/v1/accounts/GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR/operations?cursor=JEdBN0FCQkNTTEY2T1BLNkJPTjQzQ1NWVzZINVdNWFpFS0lKNDM3Mk9QM1I0M0VEUFRQMjVJR09SLQAAAAAAAADmAAAAAAAAAAFjZDhhYjYzYy1mMjE4LTExZTgtODk0YS0wMjQyYWMxMjAwMDI%3D&limit=20&reverse=true"
},
"self": {
"href": "/api/v1/accounts/GA7ABBCSLF6OPK6BON43CSVW6H5WMXZEKIJ4372OP3R43EDPTP25IGOR/operations?cursor=JEdBN0FCQkNTTEY2T1BLNkJPTjQzQ1NWVzZINVdNWFpFS0lKNDM3Mk9QM1I0M0VEUFRQMjVJR09SLQAAAAAABgnJAAAAAAAAAAA3MDNjNTYxMC0wNDIyLTExZTktYjFlYi0wMjQyYWMxMjAwMDI%3D&limit=20&reverse=true"
}
}
}
```

Start by repeatedly running the account operations endpoint shown in the issue with the same cursor, limit, and reverse parameters, and compare the returned records. Trace the endpoint's pagination and ordering behavior; done means identical requests consistently return the same records and count.

Written by the indexing model from the issue text.