So I created a hunter and tamed two pets , first a Ravager, then a Wolf. I summoned the Ravager and entered the arena; it showed up as expected without any issues.
https://prnt.sc/ujI-_mQhv6xN
Now, this might sound a bit dumb since we all know pets are saved server-side, but I used to be on a server where everyone had problems with their action bar spells resetting after each login. I suggested they remove the Read-Only from the client folder, and surprisingly, it fixed the issue. Maybe it could help with your problem too. Worth a try.