Button combination and "Null"message

HI everyone!

I appear to have a button combination that makes a setting in retroarch being set to “Null”, or “slowmotion”, but I almost always get the first message to appear in yellow text in the bottom left. Whatever the case the game I am playing will slow down to a crawl and become unplayable. I’ve looked in retroarch hotkey binds and in device 1 inputs but I have no hotkeys assigned to anything what could cause this.

I have a n64 3e party controller (tribute 64) hooked up to a Blissbox and the device is registered under “Bliss-Box 4-play N64”. Whenever I hold C-Up and then press the right trigger the above happens. Those inputs have no other assigned keys to them, So I have no clue what to investigate next.

Any help would be appreciated!