Rift scanner keeps failing during bosses

[Rane.7134]

I have a problem with the rift scanner not working properly when at a boss encounter when there is something to close with it (big white circle under the boss). I press 'F', my char raises the scanner and immediately drops the hand and nothing happens. Sometimes this happens when closing a rift as well. I've checked that I'm not in combat at the time.

Edit: Might be operator error in the end. Disregard this for now. I'll keep trying.

Edited March 5 by Rane.7134

[Gop.8713]

This happens to me sometimes when I have a random mob targeted. Clearing target allows me to do the thing . . .