REST RollUps from 5.2.4 to 6.0.0 -- migrates 0 entries (probably due to PersistenceException)

Trying to process REST rolling upgrades using latest infinispan server 6.0.0 snapshot as a TARGET node and old 5.2.4 server as a source node.

20 entries stored on source node successfully,
recordKnownGlobalKeySet does not nothing (this is ok) REST is able to provide full key set
but then,
operation "synchronizeData" using "rest" issued on new node is returning:
14:05:23,252 INFO [org.infinispan.upgrade.RollingUpgradeManager] (pool-1-thread-1) ISPN000216: 0 entries migrated to cache default in 30 milliseconds
however, there is 20 entries stored in the old node.

Please see attached file for more detailed stack trace.