3DPrinting

i've been battling this wrinkling phenomenon for weeks. it shows up at random, and i can't figure out what i'm doing wrong. i've changed layer height. i've checked the z-offset of the extruder. i've lowered acceleration to 1/10th of normal. i've lowered the flow rate. i've raised the flow rate. i've cleaned the plate with soapy water and IPA. i've checked for bumps on plate and the bed. i've flipped the plate over. i've done automatic and manual levelling. i've redone the bed compensation calibration like twelve times. i've moved and rotated my print. i've tried different colours, materials and makes. i've dried the filaments to under 10% humidity. i've switched extruders. i've placed the printer on a mass damper (a 25kg slab of concrete on top of a 2cm thick rubber granule mat). the last thing i did was physically holding on to the extruder as it moved (that's what that thicker band in the top left is).

this can happen no matter how far along the print i am. it can be fine for the first 300 layers, then start happening on layer 320 and be so serious that the extruder hits the wrinkles and loses its place on layer 330. i've been sitting there staring at the printer as it does it and the filament just seems to... come out like that. it doesn't expand or anything. and sometimes it doesn't happen at all. the only common denominator is that all the prints that it happens on have large horizontal planes.

i don't think this is caused by overextrusion of the first layer, partly because it never happens on the first layer, and partially because i did a bed adhesion test:

yeah adhesion is awful here. i forgot to actually clean the plate this time. but the part in the middle is the only one that matters, and that is clean. if anything that looks like underextrusion. i just don't understand. i think i need professional help. first from the 3d printing community, then from a therapist.

here's my bed compensation matrix, for reference: