session.ExecuteScript("wheel_left()"); does not work under chdkptpremote.net.
It's good that you found a solution, but from the CHDK POV, it really shouldn't matter whether the script came from chdkptp or chdkptpremote.net. I'd again encourage you to check the status, it seems likely something is wrong somewhere else.
I don't recall exactly why I used post_levent instead of the wheel functions in the GUI, maybe because some ports didn't implement the wheel functions, or because the levents work on some cams without a wheel. Neither of these applies to your case, since sending wheel_left() works in chdkptp.