Looking at your pics, it looks like your T-stats are in diferent locations. Could it be that one is in a warmer area than the other? That is what happens in my old drafty house. T-stats have to be set higher so the house feels like the right temp. and some areas feel warmer. With the power seeming to be OK, thats all I can come up with without blaming the equipment. (I find equipment faulty a lot less than pilot error or bad install.) Good luck, be sure to post the solution. You've got my curiosity up now.
CDC