Raspberry camera cable can cause any kind of troubles to gps, you could try disconnecting camera and see if the problem is solved.
Could that be my original problem, I have installed 4.0.4 RC1/RC2 from 4.0 dev that I think I read is 4.1?
I have tried running it on the bench without the rpi on and I can see same behavior. It’s like this fw are relying more on the GPS speed than what Ive seen before. When the issue occur I have high speed variance, at least what I think
Testing indoor with fairly bad reception the gps-raw and global-pos-int follow each other pretty well when running 3.6.12. (without updating parameters after downgrade) no pos-int runaway as I seen in 4.0.4RC1/2
Another finding I got is that the 3D printed TPU box I made for the GPS seems to interfere with the gps reception. Got less variance in GPS speed signal just by taking the lid off.