Sounds like you have a intermittent switch issue

i'm not sure if the heads use optos or microswithes but if they are micros adjust by either bending the actuator wire or adjusting the switch position so they better register that the ball is there. if optos give them a clean and check they're working ok

Another test with optos, put the pinny in switch test mode and then walk away, come back 1/2 hour later to see if it registered an opto being actuated - this happened on my STTNG and it turned out I had an opto LED intermittently registering, replaced the IR LED in question and all good now