This bug is not new and is known by the devs, but since I was unable to find the bug report for it, there is it :).
So the bug is with the radar antenna pitch speed, it is fine when going down, but very slow when going up.
The radar scans 120° and 4 bars by default, on the left of the radar screen, you have the pitch rule, the commanded pitch (4, 2 or 1, depending in the select bar scan number) and a line showing the real radar pitch.
When commanding the radar to look down, the current line scan is finished and then the radar jumps to the commanded pitch but when looking up, the radar scans each line going up until it reached the commanded pitch, and that can be very long.
Here is a track illustrating the above, in it I have 3 planes in front of me at 80nm and you can see that the real pitch takes a long time to go to the commanded pitch.
radar_pitch_bug.trk
Ask me if you need anything more :)
Tikas, you owe me a meal.