Whenever I use sample one to make a MIDI track, it frequently plays random extra notes that are not programmed into the MIDI track. I have made sure that each sample is restricted to it's particular key (ie. one of the samples is set to play only on C4, no higher, no lower; C4 is set to be the only key that will play that sample). Even when only one note is written into the MIDI track (like C4), other random notes are just playing whenever they feel like it (like D4).
Using Studio One 3 Artist