Talisman Windshield Washer Heater Fault

Sounds like a faulty heater, alright. Freezing nozzles despite proper fluid points to that. Have you checked the wiring and plug connection to the heater itself? That's a common culprit. Sometimes they corrode or come loose, causing an intermittent or complete failure.

Good call on the wiring. Where exactly is the heater unit located? I want to check the connections before I start tearing things apart.

It's usually integrated into the washer fluid reservoir or very close to it. Check around the base of the reservoir and trace the wiring from the nozzles back. Given the error code and frozen nozzles, a dodgy connection is highly probable, but a faulty heater element can't be ruled out entirely without proper testing. If the wiring looks good, honestly, I'd suggest a workshop visit. They can properly diagnose it. For reference, I just looked up the part and its install and it seems like an easy fix if you know what to look for, but I don't recommend fiddling around if you aren't confident. It seems like this could also cause issues with other sensors on the car.

Thanks for the advice! Ended up taking it to the shop. Turns out it was indeed a corroded plug connection to the washer heater. They cleaned it up and replaced the connector – cost me 95€ all in. Problem solved!