Problem resolved.
Up until now, I have not paid any attention to the display settings 'Accelerate 3D Graphics' as it has never done anything for me in the past.
I decided to review the display options and try each setting, just to make sure if this may or may not help.
Surprise when having enabled 'Accelerate 3D Graphics' and leaving disabled 'Use full resolution for Retina display'
This resolved my problem.
Sorry for the annoying read.
I hope this helps someone else.
Cheers
Barry.
