v box issue

i have 2 tv and 2 similar sat receivers in one room, when i'm using both i put card in front of one of the receivers so the remote only operates one. last night they started behaving strangely when changing channel or trying to access the menu, at first it was only one receiver, then both played up. i tryed swapping out one of the receivers=no different. problem traced to alsat v box with it on or in standby it interferes with remote signal.