Unlucky and I hope they sort it for you. My experience of 4iiiis is it one of the more robust/ stable power meters Ive had not that I have much to compare it to (a Favero B Pro S, Limits and a Avio Powersense). My sh1tmano cranks failed with the problem that doesn’t exist just before Christmas and I put it back on the bike a couple of weeks ago expecting battery degradation but it was fine.
Last winter the bike was stored after rides in my parents garage in Scotland for about 5 months (probably stayed +ve deg C figures though, outside would be below 0deg often). The Scottish roads seem to destroy things at that time of year (it was probably the precursor to the crank failure 8 months later) yet the 4iiii never missed a beat.