I am currently using sibelius 6, and i have transcribed a 6 page piece, but when I play it back, I seem to get some sort of fluctuations. By fluctuations, I mean that when I play it, certain beats are shorter than others and it literally cuts miniscule sections out. This is really hard to explain
For example, there is a long, simple c maj. arpeggio spanning 2 octaves, on either hand (piano). When it is played back, small parts are "rushed" and even the metronome, when clicking along, rushes and 1 click does not last as long as the others. This would happen every 3 or 4 bars and is extremely annoying. I tried playing my piece in school since they have sibelius 7 and it worked perfectly without any fluctuations, but as soon as i play it at home it doesn't want to play properly. I originally transcribed this piece on Sibelius Student because I have a copy of it but it is currently installed on a broken computer and I cant activate it, so I thought that that might be the reason, but sibelius 7 plays it fine. I'm not sure what the problem could be, maybe in my computer speed, but my notation is completely correct and I made sure of that before posting this 
Thank you very much.