Use a logic probe or oscilloscope to check upper level logic signals feeding to the predriver for the coils that are locking on. The type of symptom you describe where the coils activate in test mode, but do not revert indicate this isn't a passive type of problem: for example, if the predriver transistor was shorted, or some other "hard" failure,the coil would be locked on continuously as soon as the game was active. The fact that the coils are actually off in test mode until called upon by the logic to fire indicates some type of upper level logic issue (PIA perhaps)