Gotta be juggernaught users.
Blooming mugs!
I plant betties myself and they're easy to avoid even without bomb squad.
Either just have your aimer down a lil lower so you can spot any flashing lights.
Or just jump backwards when you hear one shooting up, if you're on core if you jumped back quick enough you will avoid it completely or just get hurt a bit. It takes practice but I rarely get hit by betties now.
Another tip is to avoid obvious spots for betties. If theres a door leading to the HQ, climb through a window or something...
Later