Just a report about the built in plugin logging.
No idea how this happened and maybe when I was trying to track down an odd 'send' occurrence but anyway, I had logging enabled.
Well, it's just taken the better part of 2 weeks of odd internal site behaviour to track this down. The admin side jquery and widgets were not functioning properly and adding or editing posts were white screening and weren't able to drag and drop. Also memory issues.
This never displayed on my local machine as the logging west enabled.
Unsure why but I eventually found the issue and once logging was disabled, the site is back to normal. Phew!