My up300 presented the typical behavior of heat creep. During printing the extruder clogged sometimes earlier sometimes later. I tried everything. cleaned the nozzle , different temperatures, different filament spools, slower, faster, played with extruder scale… with planned interruptions… everything didn’t help… even tiertime support. but i figured it out myself! There are two screws on the extruder motor (under the plastic cover) that hold the small heat sink. One of the screws was loose. There was also no thermal paste. After I eliminated these two weaknesses, everything works fine again.