Context Menu Shell Command: "Application not found"

Question

I've written a context menu shell command to open my WSL distro, Ubuntu 18.04, in the working directory. It works on my desktop, but trying it on my tablet yields the error "Application not found" from a small window titled "Explorer.EXE". The registry file and installation instructions are in my repo. If you want to test it manually, here's the shell command it places in HKEY_CLASSES_ROOT\Directory\Background\shell\WSL\command:

ubuntu1804.exe run "cd `wslpath '%W'` && /bin/bash"

What I've tried:

• Running it on my desktop. It works.
• Running the shell command from cmd. It works.
• Adding ubuntu1804.exe to the system path (I also tried the user path)
• Adding a different program to the above key, cmd.exe. It works.
• sfc /scannow (in both normal and safe mode)

I suspect there's something I did while developing the command on my desktop that makes it work there. I haven't a clue what though.