Thread locking adhesive ("Loctite") is easily undone by heating the fastener with a soldering iron.

If you want a lockwasher that doesn't dig into the surface, and works better, get a Nordlock; Two washers with facing wedge surfaces, as the bolt tries to unscrew, it tightens due to the wedges. I had a first gen Dahon folding bike with a folding crank that the bolt was always coming loose, regular lock washer didn't help, a Nordlock worked.