1,000,000 bps (1Mbps) seems low for a FHD stream. What bitrates did you try? Did you try increasing it to 10,000,000 or even 30,000,000 to see if that makes a difference? I'm running 1920x1080 @ 20 FPS with no major artifacts using this.

The alternative would be either changing resolution or trying to switch to a different codec such as H265 or VP9 (which appear to be supported on the VOXL2 by just searching the gst-inspect-1.0 output), but that would require changes to the voxl-streamer source.