Contrary to codamedia's reply, this issue with pedals dying is known and discussed, and people have found a solution for it:
https://www.thegearpage.net/board/index.php?threads%2Fhelix-lt-pedal-sensor-issue.2307568%2F
After a rather uncaring reply from the support ticket crew for Germany, i was pointed to find a service center in my area and call there, even though i already had a ticket. Them charging 90€ per work hour, i already imagined having to loan money to pay for this repair... Luckily there are other options, even though for a pedal that was barely used and died after 3 years just because Line6 decided to use a cheap component to save a couple of cents, it should still fall under warranty.
On my Helix LT, the emitter LED is non-functional, but the receiver works fine. So i'm gonna buy a nice little infrared LED replacement and fix it myself, for a total of under 10€ (estimated).
I hope that some other soul who has the same issue here, sees this and finds it helpful.