So status update, i sent it in (within the last month of warranty)
i sent it away shortly before corona lockdown, i received it back a couple of days ago.
they “fricking” didn’t change the broken finger print sensor.
They wrote they tested it, and it worked so there was no need to exchange it.
Damn it. Thanks for nothing.
Thanks to everyone above who suggested potential solutions.
I will now experiment with:
Just want to register that the poor performance of the fingerprint sensor is, sadly, what will probably prevent me from purchasing a phone from fairphone in the future. The lack of response to the many people reporting similar issues, and help(less) help I got from contacting tech support about the issue are sadly the nail in the coffin. It’s too bad! It’s a great concept for a a product, and I support very much the values. But it has to work, and work well - and if it doesn’t, I need to see the company responding in a timely and meaningful way. 
Just an addendum
I have used clear nail varnish on cracked screens and I would do that to my fingerprint sensor if it became cracked. I consider varnish better than tape.
Hello all,
I also have a damaged fingerprint sensor, a deep scratch/pit is visible now. The sensor is always very hot and battery life has decreased to one third of what it was before. Likely some internal short circuit.
Could someone confirm the phone working properly without the fingerprint sensor physically installed? I don’t want it to lock up during boot or normal operations.
In the ifixit link mentioned above the sensor is indeed shown as a separate part, but it seems to be glued in place so I don’t want to take it out and then have a non-functioning phone.
If anyone could confirm they have tried this that would be great.
Thanks,
Roeland