Ultimaker II issues

I'm using my Ultimaker II a lot and I'm taking good care of a clean nozzle.

Now I'm starting to get underextrusion issues.

1. I cleaned the bed of any glue stick residue
2. leveled the bed
3. cleaned the nozzle using cold pull until I could see through
4. Extruder tension was at minimum, I tightened it until the indicator was in the center

The issue is still there. Just with a bit more skipping then before
It started last week with an object that requries lots of retraction and happened after hours of printing.
Usually my objects need no or nearly no retraction. So I didn't think much about it.
How it happens in a perfectly cleaned and recalibrated printer within the first layer.

Next steps
I fear my PTFE liner may be completely used up.
I did order 2 new ones but since they get delivered with FedEx, they may not reach me.
(No delivery after work hours and no possibility for me to pick them up.)

I'll loosen the extruder tension again and redo the cleaning.
Maybe I just over-tightened the extruder.

Results
The underextrusion returned within minutes in the first layer.
I lowered the extruder tension and set my first layer to run at 50% speed until my replacement parts arrive.
This helped a lot.