I'm using Studio One 5, trying out different CTC-1 configurations, generating mixdowns to listen on other systems. It seemed that for some (but not all) configurations there would be a loud BANG! at the start of the mixdown. (I do have Ampire on one of the tracks.) To my irritation, the BANG happened on one of my most-preferred configurations. But I wondered if it might not be the configuration that's at fault, but something else about Ampire: perhaps the BANG happens if I had last stopped playback in the middle of a guitar phrase. So I played a section that had no (Ampire) guitar, then did another mixdown. No BANG this time!
I'm not certain this is guaranteed to work; for all I know, it could be happening at random; but I could believe that stopping Ampire in mid-flow might not be a good thing. (I'm sure I've read elsewhere that the BANG can be caused by junk being left in the audio buffer from earlier processing.)
A while ago (in Studio One 4), I had some songs where the BANG seemed to happen on every mixdown - to the point where my "fix" was to add a few seconds to the beginning so the **** thing would have died away before the music started, and I could chop it off in mastering. A sure indication of "trouble ahead" was if there was a BANG when I opened the song file - the only time it would happen within Studio One itself. I don't think that's happening in my current song.