2. They shouldn't be algorithms, they should revert back to the start or end of the list if that makes sense. 

By algorithm, I mean what effect is basis of your preset in those positions? E.G. Shimmer? Ultratap? Diatonic? CrushStation, etc?

I also forgot to ask, how are you using MIDI to change presets?  Are you using the Program Change, or are you using CCs to scroll and load or just scroll?  Just trying to narrow it down, so we can try to reproduce it.