bitcoinrpc.authproxy.JSONRPCException: -342: non-JSON HTTP response with '500 Internal Server Error' from server

Hi, I'm using bitcoinrpc to fetch data using multiprocessing in python (20-40 processes at a time).

I'm frequently getting these errors:

```
exception catched by line 107: Traceback (most recent call last):
File "mainF_v2_4_blocks.py", line 66, in block_processing
block_hash = rpc1.getblockhash(block_height)
File "/home/user/btc_rpc_1/btc_rpc_venv/lib64/python3.6/site-packages/bitcoinrpc/authproxy.py", line 139, in __call__
response = self._get_response()
File "/home/user/btc_rpc_1/btc_rpc_venv/lib64/python3.6/site-packages/bitcoinrpc/authproxy.py", line 179, in _get_response
http_response = self.__conn.getresponse()
File "/usr/lib64/python3.6/http/client.py", line 1321, in getresponse
raise ResponseNotReady(self.__state)
http.client.ResponseNotReady: Request-sent
```

```
exception catched by line 107: Traceback (most recent call last):
File "mainF_v2_4_blocks.py", line 66, in block_processing
block_hash = rpc1.getblockhash(block_height)
File "/home/user/btc_rpc_1/btc_rpc_venv/lib64/python3.6/site-packages/bitcoinrpc/authproxy.py", line 136, in __call__
'Content-type': 'application/json'})
File "/usr/lib64/python3.6/http/client.py", line 1239, in request
self._send_request(method, url, body, headers, encode_chunked)
File "/usr/lib64/python3.6/http/client.py", line 1250, in _send_request
self.putrequest(method, url, **skips)
File "/usr/lib64/python3.6/http/client.py", line 1108, in putrequest
raise CannotSendRequest(self.__state)
http.client.CannotSendRequest: Request-sent

```

```
exception catched by line 107: Traceback (most recent call last):
File "mainF_v2_4_blocks.py", line 67, in block_processing
block = [json.loads(json.dumps(rpc1.getblock(block_hash), use_decimal=True))]
File "/home/user/btc_rpc_1/btc_rpc_venv/lib64/python3.6/site-packages/bitcoinrpc/authproxy.py", line 139, in __call__
response = self._get_response()
File "/home/user/btc_rpc_1/btc_rpc_venv/lib64/python3.6/site-packages/bitcoinrpc/authproxy.py", line 187, in _get_response
'code': -342, 'message': 'non-JSON HTTP response with \'%i %s\' from server' % (http_response.status, http_response.reason)})
bitcoinrpc.authproxy.JSONRPCException: -342: non-JSON HTTP response with '500 Internal Server Error' from server
```

Here is `timeout` setting my connection string:
```
rpc1 = AuthServiceProxy( "http://%s:%s@%s:%s"%(rpc_user, rpc_password, rpc_host, rpc_port), timeout=86400)
```
and entry in `bitcoin.conf`:
```
rpcthreads=400
rpcworkqueue=1600
rpcservertimeout=7200
```

What can be the cause the above error? Any suggestions how to handle it? or do I need to change timeout settings?

Thanks.