Not able to submit transactions in queue

I am getting error every time I submit transactions in queue.

I have mass unfollow, thread builder, mass creator coin buy/sell feature in my app which used to work perfectly few days ago.
(Users were even able to make 5000+ unfollow transactions without any problem)
But now, the second time i submit a transaction, I am getting this error
```json
{
"error": "SubmitTransaction: Problem processing transaction: VerifyAndBroadcastTransaction: Problem broadcasting txn:
BroadcastTransaction: : Server._handleTransaction: Problem adding transaction to mempool: : tryAcceptTransaction: Problem
connecting transaction after connecting dependencies: : ConnectTransaction: : _connectSubmitPost: :
RuleErrorInputSpendsPreviouslySpentOutput"
}
```

Any idea why this is happening now?
@diamondhands0 @lazynina