I cleaned a sticky score reel on a new (to me) Gottlieb 2001 last weekend. The sticking occurred at the 9-to-0 transition when the switch was exerting its highest pressure. But the real issue was old gunk (once lube) between the moving metal actuator of the score reel and the metal chassis of the score reel itself. The geometry of the switch arm was increasing the pressure on those gunky metal surfaces during the key switch transitions.

I kept taking out the score reel and cleaning those gunky surfaces with alcohol and Q-tips. I would put the score reel back in, it'd work well for a while, and then some additional gunk would work its way onto the operative surfaces and the actuator would start hanging again. The switch transition was exacerbating it, but the real issue was getting ALL the gunk out of those crevices. I was avoiding total disassembly of the score reel, but as a result I had to clean it about 15 times.