JGroups subsystem may deplete its threadpools with all threads deadlocked (waiting for credits). Requests to this node are not handled, the node itself may issue requests but it never gets the response, which results with TimeoutExceptions from Infinispan.
In this situation the node still stays as a part of the cluster.
This problem applies both to embedded and server mode.
Workaround is increasing UFC.max_credits and MFC.max_credits to high value (suggested value is 10M) or removing these protocols from the JGroups configuration at all.