Ok - got you this time.
I might have a HH schematic here in the pile.. as usual though, they are in the shed with no power and I don't get home till dark.
What should be happening is that the zero position on each reel is engaged.. the 100's reel is engaged to reset by the 9 position on the 10's reel and so on.. that tells the machine that the game is reset. What I think is happening here is that the relay that pulses the score reels ( should be in the backbox) is not engaging properly.. I THINK its labelled DB... it needs to be open when all reels are at zero... if it stays open then the game assumes the score reels are reset ( am I making sense?).
This relay talks to a switch on the score motor telling it to stop because all reels are at zero.
It the problem comes and goes like you say then im afraid its a very fine adjustment that required.. could be a dirty contact or misaligned switch that is slightly out.. check with your DMM
