I did check and both were the same except that Vegas 13 was set to use Windows Classic Wave driver while Vegas 14 was set to use Microsoft Sound Mapper. However changing Vegas 14 to use Windows classic wave driver didn’t fix the problem.
One thing that I have noticed is that I can can sometimes play just the sound effects clips over and over again without volume cutting out but if I play the last 20 or 30 seconds of the project then go back to the beginning and play the sound effects clips then the volume almost always cuts out. When I first started trying to track this down it seemed that every time that I played the sound effects clips it would cut out, now it is appearing to be more intermittent.