Weird problem for sure. I would start by disconnecting the 1/4" line to the relay valve and test it as you are driving to rule out the actual sound and vibrations created from the horn itself. Getting the codes that being logged would be good to acquire too.
Thanks everyone for the helpful responses, and for a few laughs from the smartasses lol. I'm really thinking it could be vibration tripping up a sensor, because I can hold it down a good 5 seconds before it even registers a drop in systems 1 & 2. And I only use them in absolute emergencies, I'm not the jerks you see in YouTube scaring people. I don't have codes, but again the abs and traction control both light up, which also causes the red check engine triangle to light up. I may try putting a temporary baffle in front of the horns to see if that stops it from happening. And yes, put it in a separate system to preserve my stock cheap air horn