MK3 Extruder problem

I bought my MK3 back in 2018 an i printed about 9,5 KG of filament without any major issue.
Since two month i start to get problems with the extruder stop extruding resulting in unfinished prints. I thought it was a problem of a clogged nozzle so i changed and it get a bit better. I ordered a new heater with a bunch of nozzles. The problem came back. I changed the heater (new barrel / new nozzle 0.4).
Still the extruder stops extruding.
When it stops it starts with the deep clicking noise paired with “heavy” vibrations on the printhead.
I tried different filaments (good german brand) wich always print very well, the filament is running freely.

I mesured the gear on the stepper motor i get readings on my digital calliper from 9.12 to 9.14mm.

I guess the gear is worn out.

Do i need a new extruder or is there another way to solve the problem? I allready have a new heater and my old one is still working.

Here what i found so far.

My printer came with the v2 heater but with the “old” nozzle installed.
Old nozzle => haeter barrel and nozzle is one piece => tiertime shop shop says they are not for the v2 heater.

The 9.5KG filament where printed with these old nozzles 2x 0.2mm and 2x 0.4mm.

When i switch to heater v2 with the new nozzle i get the extrusion problem.
New nozzle => heater barrel and nozzle a two separate parts

I raised the temperature with v2 heater by 5° without any luck i cloud see the extrusion problem even by simply extruding material (via load function).

I now order some old nozzles to be able to print again and i may try again the “new heater” with much higher temps.