Hi joop,
thanks for your reply.

I was using ABS-Slush on the plate to make the print stick better. Since i did not clean up the surrounding area after a previous print, i had bubbles of ABS on there.

I am using the original Hot end.

Settings:
Image 1

Image 2

I am using the german version of cura so, if anybody has a problem reading something, i will try to translate :-)