I have also not noticed a pattern. I usually play with 3 or more team mates and almost every session we encounter this loop. I have never ever noticed it, however, on another player (external to our group). We usually log in at the same time in one server when we start the session.
The bug does not appear to be a link between two players. Let's say we have players A, B and C. Upon logging it player A may say player B being in the loop whilst player C won't. In the same time player B will not see player A being in the loop, even though player A sees player B being in one.
So to sum up - it is a random occurrence in which in every player's screen different players are bugged with no apparent logical connection.
I have noticed that there is no set length of time that makes this bug disappear - it varies from several seconds to tens of minutes.