I seem to keep getting to the same point in a render and then it goes no further. I’m basically using factory settings but have increased my output to 6600 x 3712 as I wish to use the image at A2
I’m not sure but maybe you’re getting out of memory? Try disabling progressive mode and see if it helps.
Other things that might help:
1- Try Irradiance Map + Light Cache combination instead of Brute Force + Light Cache
2- Reduce Light Cache subdivs amount
3- Use GPU (if you have a good one) instead of CPU
4- Check in monochrome mode if you have backfaces visible to camera