When the AMS refuses to pullback the filament during a print or an unload, I have successfully managed to make it work perfectly fine by just power cycling the X1 Carbon. I don’t quite understand what is happening that is different when it starts up compared to the unload but this has solved the issue for me at least 5 times in the past couple of days.
Did you open a support ticket already ?
Yes I did and I believe they added the fix in a patch.
I think it’s worse than you describe.
I believe that the bug is that when the AMS runs out of filament, instead of using all the filament as it used to do. It tries to pull back the filament and obviously can’t.
What it used to do was correct, use all the filament and then request a reload of filament through the AMS