Running presets issue/ possible pitch control?

Hey I recently finished building my sampler box and managed to get my presets running, but there's a problem. When it boots, I'm only able to cycle through the even numbered presets and not all of them in order. For example, when I turn it on, it would play preset 0, 2, 4, etc. But to access the rest, I have to kind of somehow cycle back or forth while the next preset is loading in order to access the odd numbered presets (preset 1, 3, 5, etc). Is there a way I can fix this? Also, I really want this to replicate a mellotron a lot and was wondering if it is possible to add a pitch control on it, and if it possible to also blend or layer presets together?