Have you used magnetic grenade before? If so you would know it only sticks for the first blast, afterwards it is stationary. So you can move before it kills you. Just watch.
https://www.youtube.com/watch?v=xSEb3y4-KP0
English
-
That is most likely a bug or lag. It's meant to stick to it's target and explode twice. I've had that happen with even fusion grenades before