The only thing I've found with Datakam / Registrator Viewer is that the software's graphical speedometer appears to be inaccurate - it does not match the speed of the GPS displayed by the dashcam, nor does it match the speed of the vehicle.
From the video above, it's hard to tell because the vehicle is constantly accelerating / decelerating and there's clearly a lag between the dashcam displayed speed & the Datakam displayed speed. This is not the inaccuracy that I'm referring to (nor is the software change from KM/H to MPH and vice versa).
However, at a particular speed, Datakam appears to be off by +/- 10%. When setting the vehicle on cruise control at a particular speed, Datakam shows varying speeds. I tested a 5km (3mi.) stretch of highway, vehicle cruise set to 110 KM/H, dashcam showing 111.xx Km/h (where xx varied +/- < 1 Km/h due to undulations in the road) for the whole section, yet Datakam reported I hit 120KM/H in multiple sections (it kept rising to 120 and falling to 106). As video evidence, this would be damning evidence against me.