If it is in fact polycrylic you can damp a rag in warm water and press it on the playfield flat. Let sit a few minutes and then try to remove. If its water based it will likely soften it up enough to remove easily and should not hurt anything under it. Key word here is damp, not soaking wet. If there are any bare wood areas you should stay away from them with water. Never start with aggresive chemicals, too much risk of damage to artwork.
Good luck. I am getting ready to do an overlay on a xenon playfield. It will get all new inserts as well and a healthy coat of clear when its done.
My black knight has a very poor clear coat job on it that looks like poly. Its so bad I dont think they even attempted to clean the dust off it prior to putting on the poly.