I have an old pair of devices on HA in version 11.6.4, they don't have GTM module, but Link Controller instead. There's an issue that sometimes, suddenly, Wide IPs configuration is changed without any human intervention, and I think that is probably due that I have Device Management Sync in Manual, and also I have Link Controller Configuration Synchronization activated.
So, my theory is that maybe I only need to have Device Management Sync configured, and Link Controller Configuration Synchronization needs to be disabled in order to prevent issues with automatic GTM (Link Controller) sync.
I'm not sure if Device Management Sync syncronize the bigip_gtm.conf file or this only happens with GTM (Link Controller) sync...
It should be , this is what is not synchronized :https://support.f5.com/csp/article/K21259300 . The DNS sync is probably what causes this as it is only automatic but if the F5 devices are in HA why not have auto sync? You could move the two Link controllers in seperate DNS sync group and this way the DNS changes will be synchronized only between them.
You still better follow https://support.f5.com/csp/article/K14977#enableSyncUI .