With a Plectrum track, a note keeps sounding until another note is played on the same string.
Assume a Sequence
{ 1 0 5:100; 3 0 5:100 }. Also assume, for simplicity, that a beat is 100 MIDI ticks. Then this sequence applied to an A chord results in:
0 note on A1
99 note off A1
100 note on A1
...etc...
Now let's introduce some randomization.
RTime 5. The note off of the first note will now be somewhere between 94 and 104, while the start of the second note will be somewhere between 95 and 105. If the values are, respectively, 94 and 105 there is a big gap. This often doesn't matter much since the previous note is probably already soft (it's a string sounding).
But when the values are 104 and 95, then end of the first note happens to fall after the start of the second note and the effect is that the second note is almost immedeately stopped:
2 note on A1
95 note on A1
104 note off A1
...etc...
In other words, several notes will sound muted. While this may be considered an interesting effect, IMHO the correct approach is to use the same random displacement for both the end of the note and the start of the next note.
(Yes, I know, you're a sax player and you didn't write this part of the code...
)