You can easily test the Z microswitch repeatability / accuracy. Write yourself some Gcode or connect to the printer with something that can send Gcode. Send the Z axis home command or move the Z to zero (where it will touch the bed or be a particular distance) and then send it repeatedly up some fixed distance and then back to zero. It should repeat. Microswitches are normally VERY repeatable.
BTW. I found almost everything that was assembled at the factory needed going over with a machinist square and the allen keys. Perhaps moving it threw something off?
I tested mine with a 123 block to be sure it would accurately move the commanded amount.
Did you try / confirm the temperatures I suggested and use the 3thou feeler gauge?
Bed adhesion is most often the zero height of which bed leveling is only one part and the temperature and condition of the surface plate.
I hadn't thought of going over everything again for fastener tightness, and ensuring it's all square, but I used a machinist square while I was putting it together.
The move itself (carrying from one bench to the other, so maybe walking 8 feet) was last April and I've printed many things with no issues. The oddities I started seeing last week that led to this post showed up then. I can think of one print that had a corner that lifted a little but was still usable.
It occurred to me after that post that the microswitches I tested at work were (1st) a different model - the ones with a roller on the end - and (2nd) the production several years ago. Although I still wonder at it, this Christmas is my sixth full year of retirement.
I haven't measured the bed temperature, but have one of those IR sensors. My feeler is a slice of A&W root beer can that my micrometer says is .0040" thick. I've tried the software that @dsage
offered, above, and had my best results of all. I then switched back to the Jyers software and printed a set of those bed level-checking squares and had some issues in spots. In some corners, there's too much plastic, a small blob. In other spots, it still didn't adhere well. That was while using the "purple school glue" on the bed.
I should point out that the filament I'm using, eSun PLA+, says that the bed doesn't generally need to be heated and I've done several prints without having the bed heat on at all.
I've cleaned the bed with water, isopropyl alcohol, denatured alcohol, and acetone, though not all at once (that was a joke). For removing the school glue, I find plain water works better than all of them, but I really go through paper towels with it.
I suppose my biggest question at this point is what exactly the Z offset in the Jyers software should be used for. While the .004 gap is almost 0.1mm exactly, I've had better results setting the Z offset a little lower than that, like .08mm, which is bit under a full thou less than .004 (.003150).
And that's all I can think of.