Hi,
we tried to set up a config according to your pictures,
but find no trouble at all.
We are using firmware:V5.3.0, APP: V1.2.10, right?
and here is a tip for you:
enable "I/O monitor" in "Settings" of our APP,
and return to Home UI to check all the input and output of S1.
this might help you to find out the reason.
please check the "left shift" input and its corresponding "L3" output carefully.