Compare registratorviewer and dashcamviewer to see if spikes are shown in both. What about the hard coded speed number value in the video?
Have compared... seems to be a RegistratorViewer issue... not observed in DashcamViewer
Also if you flipped upside down and it works better I'll have to see what the default antenna placement is
Currently, the GPS antenna is sitting on dashboard with writing facing up.. I believe when it is stuck to the windscreen it is considered upside down, which is the way i had it in the first place.