We have noticed an issue on PXC when we have 30GB of buffer pool and the option innodb_buffer_pool_restore_at_startup enabled so the buffer pool is warmed up quick during startup.
When the node joins (state JOINER ) the cluster before the buffer pool restore is done reading all the pages it had loaded last time cluster flow control will be paused and the whole cluster will stall as the newly joined node is not able to keep up due to lack of io which is being consumed by the buffer pool restore operation. In our case with our workload it may stay stalled for 4-5 mins.
It may not be a bug but it would be best if it was possible to have the buffer pool restore operation complete first and then the wsrep continue joining the cluster or the other way around. Now percona server's innodb_buffer_pool_restore_at_startup and wsrep are oblivious to each other causing the issue described above.