Thanks Mario....I'll give this a try alongside the track freezing suggested by Brian.

I think the best guess at the moment is that the audio quantising is the culprit,as it's the first time I've used this technique,and as I mentioned,I carefully located the point at which a very audible mute occurred in the master track and narrowed it down to one guitar stem exactly at the point where I had moved an audio transient from it's original location.

When I returned it back to it's original location in time,the issue on the master was removed when this new version was mixed down.

I have another related question which I'm going to start a thread on,on this forum.

Cheers!

Dell Inspiron 5748
iPad Mini.
iRig HD2.
BIAB,RB 2019,Cakewalk,Auria Pro,Cubasis,Garageband,Sampletank.
Lots of VST,DXi and FabFilter Pro Bundle.
Amplitube,BIAS FX.
Behringer MS20 Monitors.
Several guitars.
Always trying to leave the audience wanting less.