r/prusa

I'm trying to print a honeycomb pattern with PETG on the Core One. Everything goes OK for about 10 layers after which there is a large diagonal layer shift of about 10mm. As well as the layer shift, the print goes really chaotic, strange and stringy. In other words, it's not just a layer shift - something else seems to be going on.

It's happened twice in a row now, around the same time in the print. I have the latest firmware 6.5.7 installed I don't have "avoid crossing perimeters" enabled. 

I see a lot of suggestions to check the tension of the X/Y belts, but I don't understand how it could be a tension issue when the first 10 layers are fine.

What could be going on?

I 3D print parts in ASA, currently on a Core One + MMU3, a Core One L and an XL2T with enclosure.
I got it to where I can consistently print simple parts, that usually have a good surface to lay on the bed. Sometimes requiring mouse ears to stop warping.
Then, there are more complex parts that have been hit or miss, or, in some cases, miss or miss…
Case A: first photo is a regular occurrence, near the bed, parts get deformed… but it’s quite random, see right side, perfectly straight.
Case B: following photos are the most common, some parts aren’t able to lay straight on the bed, they need supports. The surface on top of the supports consistently warps, this makes parts unusable… I’ve tried soluble supports and straight ASA supports.

Does anyone have any tips to what is causing this and/or how to fix it?
I’m not sure if it’s from the current ambient heat, although the A/C is usually on, or if I’m printing too fast..

Its not printing how it use to after I did a calibration.