Thank you Lusche. The 250 on the dar surprised me. Most vox quoted on a NOE is below 100 or 75 and that was usually for both dar and radar.
That's why it's always better to look up things for yourself, if possible. There's a lot of conflicting and often incorrect information put out on the game channels. Arena and object settings can be checked at any time give you a wealth of information, from object hardness & downtimes, to radar & base warning distances.
On number 3. Its when the red guy disappears into the ground and usually occurs on land with rolling hills. Happened last night again but it is not something I see more than say once or twice a tour.
This is not a game design feature as such. On his screen he's flying just above the ground. Simplified spoken:
The game does some kind of short term prediction of his flight path, and his actual flight path on his screen can be slightly different from that. Usually this difference is too small to be notable, but if his connection is really 'laggy', this difference can be great enough to cause the effect you described.
But like you also noticed, this is quite rare and significant only in certain circumstances.