The self triggering reduced with those inputs disabled.
But not eliminated - it was happening once every 50 seconds on Gain 8 Threshold 1.
I also tested disabling input 1 (kick) because that's the input that is next to self trigger if I disable input 17.
Disabling input 1 also reduces self triggering on input 17 by another exponential amount, almost to nothing. Perhaps every 5-10 minutes for an aftertouch.