This video will tell you everything you need to know about my issue. I searched the forums and could not find a fix or anyone with the same issue, so if I missed something feel free to please link me to that post if it has a fix or whatever:
Basically an instrument will just get stuck and won't change what comes out of the on-screen or midi-keyboard input from time to time, and I have to restart music maker every single time it does this. It's irritating and I'm wondering if there's some simple fix for it that I'm just not seeing.