We observed nodes locking up on Azure and OVH. This is output captured from a run on OVH with Rick's cache locking branch (https://github.com/corda/enterprise/tree/parkri-cache-locking).
A thread on the receiving node holds a lock in the PersistentMap, while waiting to read from the DB, see stack-trace below.
A different thread is likely holding a lock in the DB, while waiting for the lock on the AppendOnlyMap.
The full stack-traces of the sending and receiving nodes are attached (node1 and node2).
sp_who2 shows suspended selects.