I bought a Ben 10 Fourarms toy (Ban Dai) which has a defective arm (the arm is loose because the screw cannot be tightened). The plastic is worn out from overtightening/abuse. I did not know this when I bought the discounted toy. Is there any way to fix the plastic so I can tighten the screw in the slot again?
Depends on the nature of the damage to the screw slot. If part of it has broken away then you may have to try and fit another screw in a different place. If not broken but hole just enlarged you have two options: Use slightly fatter screw or drop tiny piece of wood into hole like small bit of cocktail stick - original screw may then bite and hold.