After removing the dual extruder from my Taz Pro (made in 2019) and replacing with an M175 v2 tool head, I noticed the probing was happening way to the far right edge of the left probe points (within less than the diameter of the nozzle tip from the very edge). And the right probe points were happening in the middle of the probe pads, so onto the screw itself in the case of the far right probe. Printing a test pattern revealed the print was not centered. The issue was the left x stop printed part (the one presumably made of Nijaflex) stuck out way farther than it should. When I compared the raw distance the stop protruded from the edge of the carriage it was several mms more than the one on my Taz Pro XT (made in 2023).
When you probe some of the points on the washer and some on the screw, you get crap leveling since the screw is not the same height as the washer. And probing the very edge of the washer introduces some flex.
I found the issue was a combination of three things. One, the printed bump stop part was too long (by about 0.5 mm), the printed part was not snug against the idler assembly (since they used the non flat part of the printed part on that side - the side not on the build plate), and, even surprising, the x idler itself was slightly different in that the distance between the frame and where the bump stop rests was smaller. All this added up to the tool head not being able to go as far left as it needed to.
Before you ask, yes, I did verify the build plate itself was the proper distance from the left side of the frame. I printed out the jig that they use to align it, and it was spot on. And I was not about to move the bed over as that never goes well and throws everything out of alignment since I am not a trained Lulzbot assembly engineer.
So I had to chop 2mm off the x bump stop and reinstalled the rod. Now it probes where I presume it should, which is usually the inside quarter of the probe point in the middle of that. Imagine a quarter piece of pizza - right in the middle of that. And it did so consistently on the inner piece of that pizza slice relative to the center of the bed. All four corners.
So, I have to ask, why did this happen? I think this is why the previous owner of my machine let it go for less than half of retail after only logging 20 or so prints. Who else has this happened to?
Here, step 4, is where this is assembled.
Nothing here is asking the user to verify that the x bump stop protrudes the required distance. If you get this wrong, you get the problems I was having. And that renders the printer unusable since you now have a mechanical issue no amount of firmware updates or gcode can overcome.
I have a separate rant about the printed parts on printers being made today being incredible poor quality as compared to 2019 and earlier. My Pro XT has some of the crappiest overextruded printed parts I have ever seen. Top finish is rougher than sandpaper. This is not acceptable on a 5500 dollar printer.