My mothers freeview is doing weird things.  While watching TV 1 the unit switches the channel to parliament.  The channel position doesn't change - just what's showing on the screen.  This changes without any buttons being pressed on unit or remote.When this happens we lose TV1, TV2, TV1plus1,tv2plus1. And in addition the sound goes on choice TV &TV4.  But then the sound comes back when you turn unit off and on or sometimes when you go up a channel and then back down.  This happens very sporadically.And will be OK for a day then go funny again.  And then function normally - without a retune.  If i try retuning while malfunctionng it will not find TV1&2 etc.  Any ideas?  Could it be possible that it is losing TV1/2 frequency group and swtching to one that is OK ie a diff freq group ie parliament.