I'm familiar with "auto-release" Morse taper spindles (e.g. on a lathe tailstock) but I've not encountered one on a drill, nor have I ever considered that one could be necessary. I wonder whether something broke off in the Morse taper socket and is now stuck. That might also explain why someone gave it a beating side-on, which is pretty pointless really in normal circumstances. If you decide to give up on the drill, I have several Meddings drills I need to get rid of...