CouchDB batch document update encountered an problem

We are testing a refurbished application of "test-network" in our company.

I have the following process within my chaincode.

Aval = Aval - amount;
 Bval = Bval + amount;
 await stub.putState(A, Buffer.from(Aval.toString()));
 await stub.putState(B, Buffer.from(Bval.toString()));

It worked fine for four months, but at some point we realized that the A data and B data were not consistent.
The A data reflected correctly and the B data rolled back.

My chaincode didn't have any errors in it, but
The peer logs show that the warning is occurring.

[33m2020-11-11 00:26:02.026 UTC [statecouchdb] commitUpdates -> WARN 10719 CouchDB batch document update encountered an problem. Reason:Document update conflict., Retrying update for document ID:B

Please let me know what the solution is.
Thanks.