Headwind MDM web panel checks the database integrity after start. This usually takes some seconds. To avoid occasional database changing at this time, it is locking access to the database.
Sometimes, for example, if the Tomcat server is restarted multiple times with a short time interval, the lock is not being released, and you are getting this error.
To fix the issue, open the PostgreSQL command line and run the unlock command manually:
# su postgres
# psql hmdm
# UPDATE databasechangeloglock SET locked=FALSE;
This should immediately continue running Headwind MDM.
Notice that even if Headwind MDM web panel fails to start, it doesn't cause the failure of all your mobile devices, they will work as expected!