Odd (and sudden) problem with bed leveling

[roykirk]

One of my three Creators developed a sudden onset of being nearly impossible to level properly. I've never had this problem before and I can't figure out what could be causing it. I use a glass bed clamped down to the build platform and then use blue tape on top of that. A couple of days ago I changed the blue tape, leveled the bed, and then went to print a model. The problem is that suddenly when the nozzle reaches one of the corners of the print surface, it inexplicably raises up about 1 mm off the bed before making the turn (I'm printing a long rectangular model). Of course the filament doesn't stick in that corner and I wind up with a mess and have to start all over. The machine hasn't been damaged, the glass plate is exactly the same, and the blue tape is the same. I'm clamping the glass plate down in the exact manner I always have. I've tried leveling the bed over and over again. I've also tried raising that corner up enough to where the filament will stick. I can do it, but doing so throws everything else out of alignment and then the nozzle starts ripping up blue tape elsewhere on the bed.

Any suggestions on not only what could be causing this but also how to fix it? One other thing I'll try later is perhaps putting some sort of spacer under that corner between the glass and the build platform. It seems like it shouldn't be needed since the glass doesn't bend, but I'll give it a shot.

[roykirk]

Well, I tried the shimming and that didn't work either. I didn't think it would.

[roykirk]

Disregard. I figured it out. A screw that holds the extruder "rail" had fallen out and the entire thing had fallen out of alignment in that corner. Problem fixed!