Are you sure it's not the pop bumper relay that's causing it. The armature might be magnetized. The pop bumper coil EOS switch should turn off the pop bumper relay. Check if it's mechanical or electrical first. Turn the game off and pull the coil plunger in manually on the offending pop bumper. Does it stick? Then test it with the game on. Does it stick, is the EOS switch making good contact and working. Is the pop bumper relay firing and turning back off when the EOS switch opens. If the relay doesn't go to off, whilst it's on, turn the game off, is it still stuck on. If it is, touch the armature, does it release. If it does, it's magnetized. Take it off, strike the metal with a hammer a few times to release the magnetism, re install it and test again.
The chances of it being holes in the playfield are nil, that game must have worked for years with the existing holes.