Unfortunately when you apply a schema with triggers those triggers run as the user that created them.
If this user is later removed as part of a cutover (unbind/bind) then the trigger breaks.

Adding a service_username/service_password into the credentials which will remain static for the life
of the db. This will allow schemas to be applied as this user.

There is a good chance I'm going to have to replace the username/password with the service_username/
service_password.
Switch the normal user to the service user. This violates the pivotal policy of "Applications should be issued
unique credentials whenever possible, so one application’s access can be revoked without affecting other bound
applications". I've never been a fan of this policy seems to cause more problems and confusion than its worth,
mysql triggers just being one example of this.
Fix backwards compatibility issue