Client alt-tabbing during the game?

I play in fullscreen, don't have any apps open most of the time because my PC is quite old.

It usually triggers when I try to place a ward or use my trinket. My trinket's binded to my mouse buttons if that has anything to do with it.

Client just randomly alt-tabs and it has costed me a few deaths which is infuriating, was just wondering if anyone had the same issue.