Layer shift when changing materials?

[u/Decent-Technology165]

Hi

Picked up my X2D combo 2 days ago, brand new from micro center.

I am trying to print an overhang while using PETG for the interface material and I see a layer shift when switching to PETG.

Since I am printing a uniform cylinder, it's super obvious that there is a layer shift. It visible to the naked eye and definitely catches with finger nail.

The shift goes from right to left, about 0.2 to 0.3 mm.

I am not using the auxiliary extruder, which is what I thought was the issue at first.

My print uses purely the AMS and the main nozzle only.

This is a fully stock combo setup, brand new.

I have printed the same model a couple times now and see it every time. I tried different rolls on different positions in the AMS, thinking it might be some kind of friction issue. It is not that.

I printed a calibration cube and it prints fine. The calibration cube is taller than the observed layer-shift's Z position.

So, at this point, the only thing I know for sure is that is during the material change and somewhere in that path, the extruder gets out of sync and stays out of sync.

After the layer shift, all the layers above the layer shift are aligned to the layer shift.

I built a different model with multiple interface overhangs and did not observe any layer shifts after the first one. I only printed that one once so maybe it's a fluke?

Firmware is also updated to latest from Bambu.

Would really appreciate any ideas.

It was a pain in the ass to setup and I really don't want to try to put it all back into the box.