Assert was:
mariadbd: /my/maria-10.6/wsrep-lib/src/client_state.cpp:256:
int wsrep::client_state::after_statement(): Assertion `state() == s_exec'

The reason was because of two faults:
- A missing test for WSREP(thd) when checking wsrep_after_statement(()
- THD->wsrep_cs().state was set to s_idle instead of s_none