This Could be a piece ofwel debris or enigszins just some lint that’s gotten caught in there. Take a look inside the gun and see if you can spot anything that might be causing this issue. Finally, it’s possible that your Scotch tape gun is just defective. With 3M VHB http://www-x.phys.se.tmu.ac.jp/cx-tes/index.php?timmsheppard567766