Dear All
I cleaned everything again, changed filament, again. At least (without retraction) I was able to print 3 pieces (rather long prints). While cleaning and taking everything appart I found that when I load filament into the bowden tube, that when I push it until it reaches the hot end isolator coupler, there is a small, but notable, hickup. it's like a small step. All components still look ok, at least visualy, not compressed, damaged or anything.
So I re-assembled, printed and hmmmm... strange things happening. The underextrusion is only happening (mostly) at the back of the print (looking from the front of the UM). Like on the heads way back it sort of compresses the bowden tube and that then ist enough to stall the flow? See the pictures attached:
Anybody had that before?
Thanks and I wish you all a great weekend!
Martin