It just shows that each run of model has unique issues that you can fix with individual solutions. Sorry but no other answer you can logically reach at this point. If it was not so, then this would ALL have been fixed and put to rest universally by now.
It's far more logical to conclude that the systems being monitored have hardware differences than to assume the scanners themselves have hardware differences. Having been inside dozens of 436 units, there are only 2 significant hardware versions--the board with the pads for C1, and the board without. And even then, other than the area around C1, the components, their arrangement, and trace layout appears to be identical throughout production. There's little to distinguish brand-new maunfactured boards from the earliest production runs, other than the C1 area.