Bed adhesion issue?  

Bed adhesion issue?

I recently got an mk4 less than a month ago. I did several days of near non stop printing with no problems. Then for some reason, im having some bed ahesion issues. I'm not entirely sure what caused it. so i'll lay out all of the facts that i know. 

I started a print and it failed almost immediatly due to a nozzle cleaning issue. i noticed that the hotend had dropped down a bit. so i moved it back to where it should have been and it got passed the cleaning issue. 

i started a new print and came back to find the hot end had dropped all the way down past the bed and rubbing down the side. After stopping the print and clearing the bed, i noticed a weird pattern on it. I think the hotend ended up directly on the plate and may have ended up melting it in a few places. see pictures here and here

I flipped it over to the unmarred side hoping that it would work. Which it does, for a bit. but eventually, after a few inches of height, the print unsticks. see examples here and here 

i tried the loadcell calibration test and it doesnt seem as sensitive as it used to (at least, i dont think it does). i have to press it fairly hard for it to pass. just a regular tap gets me about halfway there.  see example here

other relevant info:

• the pei sheet is cleaning with 90% ipa after each print
• using polymaker cospla
• default pla print profile in prusaslicer. 

I'm not sure what to try next. any help would be appreciated. thanks!