Garageband sound dropping in and out

Recently my sound in Garageband keeps dropping in and out randomly. Sometimes the whole track will drop out for a few seconds, other times just the main vocal will drop and the instrumental tracks and backing vocals continue. It even happens when I bounce the track and export it. I have uninstalled Garageband, updated to the latest OS, then reinstalled the latest version of Garageband, but it's still happening. Any clues as to what the problem could be? I have couple of plug-ins installed. Could they be causing it?

Thanks in advance