Probably most useful in this case is to have the scene file - it can uploaded via private uploader (details on https://help.c4d.corona-renderer.com/support/solutions/articles/12000033461-how-to-report-issues-c4d).
Just as a test, if you are using photographic exposure overwritten by a corona camer tag, try to swith to photographic exposure in the main render settings also. Don't ask why, for me it worked ;)Greetings,Moritz