I was able to duplicate this a couple of times.
When doing a remote backup to a standby pbx, you can restore to the remote machine and you have to make sure to exclude nat settings in order to not break audio.
If the primary server has a chan sip ip address, the restore to the backup server restores that ip address, but the general sip ip stays protected as instructed.
I believe it should be protecting both general and chan sip.
Not sure if this is by design.