Hi, this looks to be the same problem I had in a dark interior in Corona 6.(Dark ceiling)
After contacting Corona support I got a workaround and also a follow-up mail that told me the issue is now fixed in Corona 7, sad to see that might not be the case after all.
I'm pasting in the workaround from support that might work, in case it's helpful for anyone else.(I never got to test it):
"I am afraid we have this issue logged already as a bug of the new bloom and glare, there are still cases where the new B&G fails when the backdrop is somewhat dark.
In your submitted scene the issue is most prevalent when rendering low resolutions or when working with extreme values on B&G (see attached), this can be somewhat resolved by shedding more light within your scene and lowering your exposure values into ranges of -1 and 1. Brighten the albedo of your ceiling material or simply increase the size of your B&G effect. I am afraid you will have to resort to finding a balance between the aforementioned parameters for the moment until this issue is properly addressed."
