Is your problem also occurring on the first score reel (leftmost)? Being the highest value it may not have a ninth position switch. That would give you an idea as to the 9th position switch causing a problem. If it's just one or two random reels on a 4 player game it's possible that there might be too much tension on the 9th position switch, but I've never seen such an issue on every single reel. 9th position does take more force to pull in all the switches but there's usually enough power as long as the reels and cams are clean. I've done hundreds and never replaced a single coil or spring. You might want to make sure that the EOS switch that breaks the current to the score reel coil, is adjusted properly. If it opens too soon, maybe the coil is letting go before getting a full stroke. You need a full solid stroke to push through that 9th switch stack.