Hey Andy, Hey Steward!
Please check out this issue, it is a very old one!
If playing with friends in a group or if encountering other players, it is possible that a character is in a constant animation loop. This maybe reflects desync between those players - since the affected character is not seen in this state by all players, only some.
You have no possibility to check if you are in a loop yourself, you need the feedback from other players.
The animation loop is the one where you are standing still and put the primary weapon on your back, the legs are not moving. And the loop is independent of the actual movement the character carries out - you can walk, run etc while being stuck in the animation loop.
Since the loop is very peculiar and eye-catching, you are very vulnerable to be seen by other players.