It actually doesn't seem to be related to the custom commands at all. It still happens if I replace the entire body of my RunCommand function with 'return false;'.
I've also tried a version of the asset that has all the references to custom commands removed (removed them in my text editor), but the issue persists!
Yeah, I'll shoot you an email! I also had two other smaller issues with the software. Would you prefer I make a separate thread or talk about them here?
Thanks for your help!