Enhanced board intermittent door sensor issues

[ThirdGenAmusement]

I have a Top Dollar S2000 running an enhanced board that seems to have intermittent door sensor issues.  I changed out the mpu battery, removed the varta and u16, set the machine up and it seemed to be fine but out of the blue the VFD would display display 'Door Open M'.  I've messed with the alignment of the sensors and finally removed the door sensor and manually put it in front of the cabinet sensor and most times the machine will not recognize the sensors in test mode 4.

I've swapped out the door sensor with a known good sensor with no difference.  Here's other things I've tried:

--Swapped out the mpu with a known good mpu
--Removed I/o cards and verified no changed using menu 4
--Disconnect all peripherals such as BV and BV interface card, 7 segment display, printer, etc and verified using menu 4 there was no improvement.
--Used an LED flashlight into the receiver cabinet door sensor does result in a solid 1 in menu 4 consistently.

Oddly, the belly door doesn't appear to be bypassed yet when opened doesn't get a tilt.  Cash door was bypassed.

The machine supposedly has never been on location.  Strips, glass, and cabinet inside/outside looks like new.  It did sit for several years in storage.

I'm considering swapping the backplane board since the door sensors go through it. Any one have a similar issue on an enhanced board machine?  Any other thoughts on what to try? 

[Jim]

By pass the belly door switch, follow the two wire door optic back to the area where it connects to the harness, make sure it is plugged in, (behind reel 1).  if the optic circuit is working, the 1/0 should toggle all the time, no interruption what so ever. 

changing a back plane only takes 1/2 hour or so, change it out and eliminate that as a source of the problem, maybe removing and reconnecting the cables will solve the problem??? 

Jim

[ThirdGenAmusement]

Thanks for the suggestion Jim!  I'll give them a try   have a great 4th of July!