As I said this was a complete show stopper for me, it simply had to be fixed ASAP. After several hours of research I came to the conclusion I had a very rear issue since I could not find anybody having the same issue. The error indicating it was something to do with fileSize, maxEntity, exceeding form control limit, exceeding the limit for a form etc..... Well it simply was not any of those. When I set an unusually high 'Maximum allowed content length' value and restarted IIS it tripped something out in a big way which could not be reverted. A light bulb moment said IIS needed to be uninstalled and them re-installed. This did fix it.
Wind is your friend