Yep, same thing happened to me at a different settlement. After saving and reloading didn't help, I just left. Came back several game days later and the issue was resolved.
Heh, this is literally a bug, involving radscorpions. Get it?
OK, technically radscorpions are not bugs, but arachnids? Eh whatev.
It happens sometimes. The fix is just to wait dor a day or two.