How is the temperature sensor on your IKEA vindstyrka?

I bought one of these, and my temp sensor seems… inaccurate at best.

I can put it outside in the freezing, and it registers minus temperatures OK. But in a cool room around 16-17, it still shows 21.

I put it in a room which is actually 21, it registers 21. It seems affected by its own operation.

I was looking for anyone else with this experience.
My initial impression was that indeed it shows a bit high in cold rooms. I’ve learned this is a very common problem for sensor engineers.

More annoyingly, when restarting it gives a single weird measurement. First it showed high temperatures, now I have a few measurements of -327.7 ℃. There are three reasons I doubt this measurement. It normally only measures full degrees and it is below the absolute freezing point (0 K).