UsenetGuy wrote:

I removed the screw, demagnetized it, replaced it, and the compass now calibrates and keeps its calibration

How did you demagnetize it?

With such a thing

https://www.amazon.de/gp/aw/d/B000WTLOB ... B7XF&psc=1

yes with a thing UlmerSpatz showed you can usually find it at any hardware store really really cheap... although there are electronic demagnetizes which like that

https://www.aliexpress.com/item/Excelle ... 4.7.VOH8Wb

wich are much better and are also cheap

How did you demagnetize it?

Something very similar to the "Electronic Watch Demagnetizer" posted a bit lower. This is a coil connected to mains. One holds the magnetized bit near the energized coil and slowly moves it away; the alternating field will end up demagnetizing the bit as it gets smaller and smaller.
(I used an underwater aquarium pump with the rotor removed...)

Thanks for the tips