Known Existence: Unknown
Using the follow command can be good in most cases in PvP. However, it does have one dangerous side effect: it can make your pet frozen. The danger occurs once the pet has entered fly mode. If this happens while following a player and they recall away, the pet will be unable to move. No matter how many times the pet is told to follow, it cannot. It can, however, go through gates when told to do so. The pets name doesn't have the "(frozen)" in it. This only happens when the pet is in fly mode and would only effect birds, mongbats, imps, dragons, drakes, and white wyrms.
Solution: The only cure for this is to get the pet on the same subserver as the person they are stuck following. If this is not possible, a GM's assistance can work.