Hi Daid!
Yes, I am sure it was a clog. It did grind the filament, and could no longer feed it, but I was not able to manually push the filament in.
Well actually, the first grind I was able to force it in manually and ran enough through to be sure it was flowing again. But then a very short print later I had another grind, repeated and then another grind very shortly after. The third time I could no longer force the tube no matter how hard I tried.
That is when I decided to open it. In the brass tube there was plastic with a indentation where I was trying to force the filament. It was clearly a plug when I heated it up and pulled it out.
How much hotter should I try, 5c? 10c? Is there any rule of thumb?