This may sound dumb but I have the same hit or miss issue with the Cool Supertac build plate and seemed to solve it by using 70$% or 99% isopropyl alcohol to clean the plate before I print each time. I have had a few times it didn’t really work well but that was my fault being lazy when I cleaned the plate.
So apparently I must have gotten lucky with the following prints because now I am having the same issue all over again even though I clean the plate completely. If I go ahead and let the print continue, the print “does not” stick to the plate and the print fails immedialy. So I am stuck now.
So I figured out what the issue is. Apparently the build plate ID square is too dark for the sensor to read, so using a really powerful magnifier I “painted in” the squares to match what is printed on the plate. Painting the squares in and the line is not easy to do. So I guess when I cleaned the plate with alcohol it must have increased the contrast of the ID square for the printer to read. With a really good black and white printer, anyone can replicate and print it to a sticky label, cut it out and place it in the exact place for the system to read. I figured this out from my original plate that came with my machine. This works and keeps the print from failing as it lays down filament
I’m having this exact same problem and verified it by switching plates. I had 2 supertack plates each of which were printing in mid-air. Switching to a bambu cool-plate (the one with the bright white id) and problem disappears. I have a label printer (unfortunately thermal), but I’m going to give that a go and see if the problem disappears on the supertack. (My other two X1-Cs have no issues with them so I’m guessing that cleaning up the lens might also help.)
Yeah I was a bit annoyed with the issues of the soft printing on the ID mark so I used a video microscope (off of Amazon for $20) that allowed me to use an x-acto to cut away the Bambu marks and replace it with white paint (Tamaya flat-white) in the recess areas with a very fine paint brush. I used 100x magnification and made sure the plate did not move as I cut away the super-tac surface. So far I have yet to have an issue in the last year since I did the upgrade. If you wish and I think it may be a good thing for the group, I will do a video of how I did it. I have one standby plate where I printed over the surface rather than cutting away the surface.
The solution you came up with works too but it needs to be on paper not thermal paper. I have seen some mods done from a high res laser printers but the QR code area comes off after a while and makes it impossible to wash the plate and keep the sticker.