I once left my old (VW not SEAT) car out in very heavy rain for nearly a week. The next time I drove it I got bulb warnings despite the bulbs all working as normal. The
problem was some water ingress in to the connections between the tail light cluster and the power cables. They went away after the car had dried out a bit.
I doubt that would be the same issue with this since the tail light cluster is different. I've not had it off on my 2020
Cupra, but my 2014 Leon, the tail light cluster never quite fit right so may be prone to a little water ingress.