Heh, I've noticed the same issue with my analogue Volkslaser Evocube 1000 RGB v3, german design - chinese built, from the same folks who make Mamba laser show SW as far as I'm aware (well its on the identical address..).
Blue and Red absolutely fine, green fading when producing straight lines. But during laser show the green seems fine apart from the very absolute last 1-2 cm of graphics shown in 1x1m show area.
I've written it off as "Cheap laser experience" and, as the folks on this forum keep warning, this expensive hobby has also claimed me with my first Kvant Clubmax 1800 unit on the way. /Sigh
What laser software you running btw?
My kit: Mamba Elements V3 & DAC, ILD SOS & LaserCam, LaserDock DAC, Kvant Clubmax 1800 (2017)