The MS-CIFS spec, section 2.2.4.32.1 states that only a single lock cancel request can be made per PDU. The Samba4 server handles this correctly, but then returns an incorrect error code when a locked file is unlocked. Interestingly, Windows servers do not conform to the spec and allow multiple lock cancellation requests to be made without error. This behavior is exercised by the RAW-LOCK-ASYNC smbtorture4 test.
samba4.raw.lock.*.async should be removed from source4/selftest/knownfail when this bug is fixed.
Reassign file server related bugs up to tridge.