According to the wiki, most aircraft are supposed to use the Raster Scanning Pattern as shown on this image found on the wiki.
https://wiki.warthunder.com/Airborne_radars
Every single aircraft that I have tested so far, regardless of nation, is not using this pattern. For the sake of simplifying, if on the image on the wiki, we assign to each vertical step the letters A, B and C from top to bottom, you will notice that once the radar finishes scanning section C, instead of going back up to A and starting again, it just reverses and scans C again but on the opposite direction.
This issue can be observed with radars that have modes that allow for more than two bars scan (vertical steps). I believe that this is part of the reason that sometimes targets drop from TWS, targets being swapped for other targets or missiles, as well as these weird spikes on speed and changes on direction you see sometimes that make no sense.
I suppose it is a bug because on the wiki it clearly states how it should be…