I had the exact same thing with my ultimaker 2 and the fans were on permanent.I got it fixed by ultimaker UK and they swapped out the motherboard.

Prints a dream now.

Did you used flexible filament successfully, which branad and settings did you used?

I have tried Extrudr.eu ABS filament with good results. The main advantage of this ABS filament is that you can print at 210/230°C Temp. Very low tempeture compared to 240/260°C of most ABS Filaments. The finish result is also good.

This was printed with Extrudr.eu Black ABS filament:

Best Regards

3d4makers.com the best filament adn very divers

Without a question: PURL Scientific. We still only use Purl at my university. Purl Scientific makes filament for many major companies they just slap their brand on.