There are stale locks that happened when a transaction failed due to a replication timeout to its peer node. The transaction contained grouped keys that were submitted to the primary owner. During execution of one such transaction, there was a state transfer, which changed ownership of these keys.

Here's an example flow:

The task executed and started a transaction. Since it was not the primary owner, it sent a LockControlCommand to the new owner. This call timed out, and a rollback was issued. The local transaction is completed, but subsequent attempts to lock this key fail.

The logs can be found here:

http://dl.dropbox.com/u/50401510/5.2.0.ALPHA3/lock/10.30.12.83/server.log.gz
http://dl.dropbox.com/u/50401510/5.2.0.ALPHA3/lock/10.30.12.84/server.log.gz
http://dl.dropbox.com/u/50401510/5.2.0.ALPHA3/lock/10.30.12.85/server.log.gz