Yes, string loop rotating around the string may happen. What is hard to determine is whether it's the string twisting or the loop actually twisting around due to inertia when shot. If the loop is tight enough it should not twist around, but it happens.

One trick I found a few years ago is before installing a loop put bowstring wax on the serving where the loop will attach. This goes against the grain and you'd think this would add some lube under the loop and allow the loop to twist on the serving. In reallity it allows the loop to be get tighter when spread (with needle nose pliers) due to less friction between the two materials (serving and loop). It also allows you to "screw" the loop up or down the serving like a nut when tuning. Once tuned then you tighten the bejesus out of that loop and it should stay put.

Wish you well.