SOG/COG not working

Hello
I've the complete qtvlm 5.12.2101 build 1 version on ios 18.5 qt 5.12.19 arm64 chip, ipad pro 12.9 2018(3rd gen), 
position always enabled with high precision on.
only internal GPS no other sources active, ais through internet off, all gribs off, class 40 polars 100%, compass sensor on, real mode, no vlm:
with NMEA on, SOG stays still on -1.9, COG swings between correct values and 359° every few seconds, no raw NMEA data is shown(gps position is correct and shown correctly, track is correct, routage works)

PLEASE HELP

Can you test with another application, like Apple map or google map ?

GPS works properly in any other app -even in qtvlm, but speed stays still on -1,9 knots, and angle swings to -359 every few seconds

That is strange.. Please check in NMEA settings that you didn't check "All sources", it should not be activated.

as said, it is not checked
SOG is -1,9, COG swings to 359° every few seconds

Can you please double check? I cannot imagine another reason. It is a switch in the internal GPS parameters.
Just tested here with a non moving iPhone, no problems.