Random Instrument Playback Switches

[JDevorMusic]

Whenever I have any large ensemble score open (pretty much anything more than 3 staves at a time), partway through playback random instruments will simply switch to other playback instruments. Once it happens, there is no way to fixe the instrument. Any suggestions?

[MikeLyons]

We'd really need to see the file and to know something of your setupbefore answering this question. Can you post the actual file? (zip it first) A picture is no use for this.