Coil draws more voltage when activated. When game loses power it would freeze up. However that would not explain it working fine in free play mode. Not so familiar with that model however could be a bad eprom. File might be corrupted. Try to replace the eprom and see if that fixes the problem. Good luck.

Slapshot model was made by shelti. Ice makes super chexx. Need to know what manufacture you have. Both companies are still around for tech support and or parts.