master stuck in not valid state
When two masters are connected to the same link one of them tries to enter a state pre-master. However this state is not compiled in the ppsi, so one node stuck there forever. It is necessary to restart a node or re-establish a link.
BUG introduced by a PPSI's commit:
2996dd7b compliance, 9.2.6.10: properly switch to MASTER or PRE_MASTER