The issue can be reproduced by following steps:
1) CacheA and CacheB in a distribute mode with numberOfOwners set to 1, so that an key can only be found on one node.
2) Use CacheA to put 100 entries using keys from Integer(0) to Integer(99)
2) Using CacheB make explicit locking on a key, and then get the value for that key, if the key is not on CacheB, it will return null.
Unit test is attached