4000000020000000 - Mysql Lock Wait Timeout Exceeded
If MySQL is not able to get a lock to write to the PDB table, then an alarm is raised after 15 minutes when the lock wait timeout is exceeded.
Occasionally, a transaction can hang for a longer time, particularly in a multi-threaded environment, and also due to some underlying hardware failure on the disk, kernel bugs, and so on.
Recovery
Restart the PDB software.