I ran pdm_publish on my "Background" server ("ServerA"), which generates some files during the process. These files were not copied to the "Standby" server ("ServerB"). If at a later point I decide to create a schema change and pdm_publish on ServerB it may not work correctly, and assume that the information doesn't exist, and try to recreate the information in the database.
Service Desk Manager configured for Advanced Availability
This is due to a limitation in the Advanced Availability design.