That just happened to me too - but it was the second or third time I removed it. Although... I might have removed it the first time or two by pulling the block out from under it. I guess I'll make a point of doing it that way.
After experiencing it several times myself I'm jumping in the thread to clarify more than I did for the in game crash reports I submitted.
I agree that the quest radar is buggy. Several fresh restarts in a row it immediately crashed when being detached. So I stopped using it.
But i'm positive it can happen with any radar and not only the one acquired by the quest. I have just continued a game of 0.5.18.2 and detached a radar and it crashed. I'm convinced it's not the quest radar because this is a tech I had rebuilt from the ground up twice. So the radar used wasn't causing a crash before the save & continue.
At this point I'm unable to replicate it with non-quest radars but am positive that the quest radar is still bugged.