Awesome and helpful troubleshooting!
I usually don’t suggest updating to newer versions of the engine unless it is a close to last resort, but version 4.5.1 has some helpful hot fixes that might help resolve your issue.
However; follow these steps and images to increase your lightmap resolution and see if it resolves your issue.
Steps to Follow
- Double click on the static mesh you are using to represent your floor.
- This will open the ‘Static Mesh’ editor where you can make the necessary changes.
- Under the ‘Static Mesh Settings’ section you will see an option called ‘Lightmap Resolution.’
- Increase this value by powers of two i.e. 256x256 or 512x512 or 1024x1024
Let me know if this helped!
Thank you,