If the loop is put on properly it should not slip.
Check and make sure the serving is tight that could be the culprit or the string has not yet settled in and is creeping.
I have never used any sort of glue on a loop.
should I just invest in a peep with some rubber tubing just to be safe?
You will get a big heck no from me on the peep with tubing.
I would suggest you get a good quality string from gibblet
