I have a similar issue here, but with a bit of a twist... I have a footswitch assigned to both a volume block and a pitch whammy block. I can get the switch to toggle between the two blocks (one goes off, the other comes on) by setting one on and one off then saving BUT I want the footswitch light to be ON when the whammy block is on and OFF when the volume block is on. No matter what state things are in when I save, it always ends up the other way around, i.e. light on when volume is on, light off when whammy is on. What am I missing?
EDIT: Problem solved, sharing for others to see if needed. The solution is SO intuitive I missed it completely.... It seems that when multiple blocks are assigned to a switch, the light follows the block that is active in the bottom section of the screen. So all I had to do was touch the switch until the Whammy was shown on screen, then save the patch. Works perfectly.