I'm on a Mac. I have a USB foot pedal which I've mapped to F18, F19, and F20. In this case, F18 is mapped to page down, F19 to space, and F20 to down (meant to facilitate reading a pdf). This works fine, but I've found there's an app where it doesn't work.
In the app PDF Expert, when I hit the pedal mapped to F20 which is mapped to down, it goes to the first page for some reason. I have no idea why! In other apps it seems to work fine. If I press the down key on my keyboard, PDF Expert doesn't do anything weird.
I will note that before using F18-F20 for this, I used ctrl+opt+cmd+shift+1-3. Same deal, they all worked but whatever was mapped to the down key didn't work in PDF Expert. It's so weird! This is what led me to use F18-F20 which ended up being the same.
Does anyone have any advice on what might be happening, or how to troubleshoot something like this? It's so bizarre.