CLEAR BOARD SENSOR message- I know you'll say "get a new one" but not an option

[eastcutty]

I bought my Rev A machine from Sears 6yrs ago and the Board sensor has never worked right. It was sold as 'new', but I should have been more suspicious when it was a few hundred bucks off list price- as months, then years, went by, I kept finding more and more 'tells' that indicated someone had had their paws inside it- (tool marks/scratches/gouges, cracked plastic sensor mounts, etc) whether customer, Sears 'repair' people, or both. Don't ask me why I didn't just take it back- money, logistics, and the suspicion that their so-called service professionals would just 'turn it back around' weighed heavily.
Most of the time I found ways to repair, compensate for, or otherwise work around glitches, mis-alignments, and busted parts, guides and such (always been pretty much able to fix anything) but a constant and frustrating problem with the board sensor gets me almost to the point of tearing my hair out. 90% of the time I want to run I have to be prepared for a battle to get it to finish, or often even start, the measurement phase. I've never gotten a higher reading than the mid-30s during the sensor check, but I'd eventually get by by 'fooling' it with taped-on white paper on the board. Nowadays, tho, I'm only getting mid-20 readings.
I expect you're thinking "blow it out" or "wipe the window" but I've gone as far as removing it for disassembly/cleaning (found cracked sensor mount when locating the screws the first time- part of one of the screw tabs was missing) to remove fine dust that had gotten inside. Since then, sensor inspections found no dust in/around the light sources or light pipe because I used scotch tape pieces to better seal the enclosure before re-intallation. I do notice that I get higher (to my max) readings when I tighten down on the roller crank but it's then too hard for the X-axis drive to push the wood thru- I've had more than my share of dealing with belt tearing and busted gears- see my other posts.
To add to the confusing aspect, it sometimes, if rarely, works fine right out of the gate- or will 'decide' to suddenly work after endless re-tries with no changes made.
So, a couple of questions now that you have the basic picture: Am I alone in this type of anguish? I use light vs dark masking which seems to work best out of everything I've tried- anyone got better ideas? I also notice occasional sudden short reversals in drive direction in the middle of length- or span-wise measurement sweeps once I finally DO get past the initial 'Check Board Sensor' battle so could all of this be circuit board related? Is there a Board Sensor sensitivity adjustment potentiometer not mentioned in the available online docs?
I haven't worked for a year and a half since my last job, have no income, and I'm waiting on the Feds to stop dragging their feet regarding my disability case, so you can see that I have NO funds available to swap out expensive sensors and boards until I stumble upon the 'cure'.
Any other DIY tinkerers out there with any insights/ideas?

Forgot to mention: 205 hrs motor run time, 21?? hrs ON time on clock.