Adhesion issues (?)  

First give your build-sheets a thorough clean.  Rub neat dishwashing detergent (Dawn/Fairy) into the surface then rinse it clean with very HOT water, dry with a fresh paper towel and handle by the edges only.

Then run the built-in first layer 'Z' offset calibration and show us the result *on the build sheet*.

Right now your 'Z' offset is too high but by how much is obfuscated by the residue on the sheet.

Cheerio,

RE: Adhesion issues (?)

I agree with @diem. I also suggest taking those steps using your textured sheet because PETG can be hard to get off the smooth sheet.

RE: Adhesion issues (?)

I hit them both with 99% IPA... but I'll try cleaning them again. I'd run that cal, but I'll try it again as well...

RE: Adhesion issues (?)

Here's the first layer cal - what a mess... I wonder if something has gone pear shaped with the tip - it's still the original one...

RE: Adhesion issues (?)

Maybe the tip has  worn shorter ...  that looks like your Live Z height is too high. 

Have you by any chance changed the build plate? 

If you were previously using a smooth build plate and you have changed to textured build plate without re adjusting the Live Z, you can end up with this sort of problem because the smooth build plate is thicker than the textured build plate. 

https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/life-adjust-z-my-way/
this is an old post but still useful.    
regards Joan

Agreed.  Go closer. At the end of the calibration you are aiming to print a single layer postage stamp sized *sheet*. It should be possible to peel it off in one and fold it without the threads seperating. If it breaks into lines it is too high, not squished enough. If it is a single sheet but with wavy lines or drag marks on it you are too low.

Cheerio,

RE: Adhesion issues (?)

Adjusting the z-offset is probably going to fix the problem, but there is another possibility. The build plate temperature is way too low. I've sliced for PLA and loaded PETG on my MK4 and the results looked like that.

RE: Adhesion issues (?)

I'll work on the z-offset. The slicing for the pattern I was printing was direct from Prusa in the MK4 upgrade kit, and the temp was fine for PETG.

RE: Adhesion issues (?)

I've tried the first layer calibration several times at this point. Either it spaghetti prints too high, or there's a brief window where it spaghetti prints and sort of sticks, or you go to low and it starts printing around the nozzle and pulling everything off as it goes. I'm at a complete loss at this point.

RE: Adhesion issues (?)

Most probably still way to high. You are still printing "in the air" thats why this strange stuff happens (sometimes sticking, sometimes wrapping around the nozzle...)

Redo the build in first layer calibration continue to go lower (increase the value displayed), take a pic, post it. This is the way!

If in doubt run the built-in first layer 'Z' offset calibration and show us the result *on the build sheet*.  You are probably still too high.

Cheerio,

RE: Adhesion issues (?)

Would you please take a picture that shows the height of the PINDA sensor in relationship to the nozzle.