This used to happen to me all the time. I used hot glue. I was using hot glue purchased from HL. the name starts with an "S" but i cannot remember the name exactly. I was using a high temp glue gun too.
Every cilp I could pull apart easily!
Finally, I bought some glue at walmart. I think it starts with an "a". Sorry I'm not close to my stash, or i'd go look. It's a clear bag with burgundy on it....
This glue rocks. I also bought the glue gun from walmart with a small nozzle.
This duo has now made my clips super strong & I cannot pull anything I glue apart.
If I do, it usually ends up ripping the fabric or making a huge blemish in whatever it was.
I hope that helps. It took me forever to figure this out! I almost stopped selling stuff b/c i thought everything was going to fall apart.