Not a clue why this happened, but by renaming your buttons name back to btnBack on screens Screen2, consumption and Cut_electricity it started to work..
Almorched_correction1.aia (3.3 MB)
P.S. I just tried to build a project with 1 component (button, label, etc) named back and it didn't work to build, @ewpatton is this a new reserved word or something else as it work at Kodular