A very frustrating, and unfortunetally reaccuring, problem that I'm having with Sibelius GPO is that during seemingly random sections, certaing parts just mute themselves automatically, even when they aren't preceded by any instruction text. This has happened on three different scores I have.
In the first instance, it was every string parts playing an eigth note rythm after switching to pizzicato. However, after the first measure of doing so, every string instrument (Violin 1, Violin 2, Viola, Violincello, Contrabass) all skipped the first eigth note of each measure until they switched back to arco.
In the second situation, there were two measures of both tambourine and snare drum playing a sixteenth note rhythm for two measures (4/4 time). The first measure is fine, and the entire first beat of the second measure is fine. However, on the last three beats, the very first note of each beat is muted. (One other problem in this same score is that at one point in the song it simply stops, but the play box says it is still going, but doesn't scroll through the score. It starts up a few seconds later, but recording play back as if it was written this way.)
In the final score, Violin 1, 2 and Viola are playing whole notes as a harmony. The notes together in pairs. The first pair is played just as it should be, but the second pair (third and fourth measure) are muted.
I can't figure out why this is happening and I've tried several things to try and fix it, such as restarting the program, changing the voice, adding MIDI messages, etc. If anyone has a solution, please explain. I don't know if this problem is because of GPO, or because of Sibelius. It's also probably worth noting that that all of these scores use all 32 available slots.