Herb thanks for the reply, I did a bit of investigating…
The ones that had the issues were done when I added ‘Neat Video cleaner’ into the mix (it’s a plug-in that reduces ‘noise’ and clean-up the video)…
So Neat video running by itself and exporting no issues at all…
Neat video by itself exporting then later applying another effect and exporting no issues at all…
Neat video + any other effect running at the same time and exporting ‘MAY’ introduce a very small stutter\freeze at some point – did it to not every video but every 2 out of 3…
The videos all had the same frame-rate and resolution so perhaps it was the amount of ‘noise reduction\cleaning’ that was needed that made the error show-up?
At any rate I’ve done a few videos now with multiple effects without ‘Neat video’ plug-in and they all seem to be fine so it seems that was the common denominator.