My gfx card: GTX 780
This issue happens on terrain (hills, painted).
The procedure.... go to terrain editor, generate terrain, go to vegetation, models, hit the PLUS key (Model 0 loads), then paint.
The trees seem to fade in and out as you move closer/farther away from them, though the fade effect is very rapid.... but it is certainly not instantaneous.
It's ACTING like LOD probably would...
I've never even visited the Settings in vegetation, let alone changed them

But now that I have... I see LOD settings are there... and under Geometry far... what do you know:
Geometry distance is 75
Imposter Near is 75
Interesting how the thresholds are exactly 75m as I measured. Mere coincidence?
I'll send the scene to the "sales" address... because I have no other.
Regards,
Ryder
"A scale model is never done. You just stop working on it."