Hi, this is a known bug, but also a nasty one. It is listed here:
https://coronarenderer.freshdesk.com/support/solutions/articles/5000516180This is one of the cases where Corona is not able to cope with "fakes" in a way that would be expected by the users. We do understand that this is very problematic, and would love to fix this, however the fix is not trivial.
I am attaching a new version of your scene with a workaround applied. Unfortunately it changes the appearance of the background reflections. Here is how it was done:
- Create a Rayswitch Material and apply it to your background geometry
- Plug the original Corona Light mtl into all slots of the Rayswitch Material
- Duplicate the original Light mtl
- In the duplicate, enable "emit light" option and disable "occlude other lights" option
- Plug this edited Light mtl into the Reflect override slot of the Rayswitch material
I hope that you can use this workaround in this case.