Getting a lot of Wsrep_rollback_local logs and failed transactions

Hi, I have finally migrated my DB from 5.7 to 8.4. Everything nominally works… But I am frequently getting Wsrep_rollback_local log entries (1 per min) on each of my 3 nodes.

I did not have this problem on 5.7… It is causing problems in my application and DB transactions are failing… frequently as a result…

Any help much appreciated