I've seen tigers do that before. IME, it's most often caused by temperature shock, but I've had a couple do it for unknown reasons as well. I've managed to save most of the fish that do this on me, but I've lost a brevis and a tanzaniae to this strange condition.
ATF are very delicate fish and don't ship well. I suspect that the fish you are getting were probably in rough shape and the stress of the trip was more than they could take. That, combined with even a few degrees off in temp when you acclimated them, caused them to go into shock. A healthy ATF heals like Wolverine and can bounce back from things very well. An unhealthy ATF tends to act just like a healthy one which can lead a new owner into a false sense of security. Unhealthy tigers die if you look at them wrong it seems.
The only exception to this pattern for me was one very healthy TATF that died for no apparent reason during acclimation after an eight hour drive. I suspect that he may have either gotten stuck in a fold in the bag or he smashed into the tote so hard that he gave himself terminal wounds. The loss of that previously thriving TATF has me flummoxed.
To sum it up, I suspect that your fish were probably weaker than they looked and the stress of the move combined with a small temperature variation caused them to go into shock.
Don't give up on ATF, just try to get one from a different vendor.