After 7 months and more than 2000 hours use, I recently experienced a similar horrible printhead clog with PETG which is unbelievably hard to remove. That jam damaged the printhead as well as one of the printcores.
I contacted my local reseller, and bought a new print head to replace the damaged one. I firstly recalibrated the printer.
The first prints were perfect. So after two days I tried to print overnight but I had to face the same experience with the new print head (dead also). Please dont tell it is normal because, obviously it is not.
I am quite disappointed by Ultimaker by now.
I don’t trust the printer anymore. I doubt the printer is still reliable. It cost me two printheads and three printcores in two weeks….