The fingerprint_targets process fails when using FIFOSQLiteQueue with: Exception: OperationalError: database is locked

[11:14:08][scan_engine][_build_targets] 39 fingerprints
[11:14:08][scan_engine][scan] Number of procs: 10
[11:14:08][scan_engine][fingerprint_targets] 39 fingerprints remaining
[11:14:18][scan_engine][fingerprint_targets] Caught exception: OperationalError
[11:14:18][scan_engine][fingerprint_targets] Exception: OperationalError: database is locked
[11:14:18][scan_engine][fingerprint_targets] 39 fingerprints remaining
[11:14:28][scan_engine][fingerprint_targets] Caught exception: OperationalError
[11:14:28][scan_engine][fingerprint_targets] Exception: OperationalError: database is locked
[11:14:28][scan_engine][fingerprint_targets] 39 fingerprints remaining
[11:14:38][scan_engine][fingerprint_targets] Caught exception: OperationalError
[11:14:38][scan_engine][fingerprint_targets] Exception: OperationalError: database is locked
[11:14:38][scan_engine][fingerprint_targets] 39 fingerprints remaining

Specific problem occurs on the fpq.get() call in fingerprint_targets()