Kubistar fuel filter heater issue

I had similar symptoms with my Kubistar. Check the cable and plug connection to the fuel filter heater. A bad connection there can cause those issues.

Thanks. What exactly was wrong with your connection? Was it visibly damaged, or did you use a multimeter?

I didn't dive that deep. I wiggled the plug, and the issue improved temporarily, so I knew it was that connection. I'd recommend a workshop; it’s probably a faulty cable, and it's better to have it properly fixed.

Thanks for the advice. I took it to a workshop. The cable to the fuel filter heater was defective. The repair cost 95€, and the issues are resolved.