Yes I am working at a bog standard resolution and I have cleared the cache, save the project to an earlier AE version, duplicate the comp and double-checked it, checked everything, quite strange ..
I am now rendering the problematic section and using a QT movie too replace it so I can get it out of the door ..
But not relieved the issue at all ..
I received the project build from a colleague working on PC with an earlier version of AE, 2015 I think, when I opened the project it has to be re-saved to my current version and there were some problems with XMP files but it made no sense .. I have rendered versions of this build with no problem yet now this problem persists ..
Shoots, Animation, Editing. Adobe Creative Suite CC2018. Sound Design & Logic Music Production.
Mac OS X - HIGH SIERRA 10.13.3
iMac 27" F2017 32Gb RAM