Hello there @leoviale!
From your provided screenshots, the first thing that crosses my mind is that your current value for rendering the reflection resolution could be a bit low, test by incrementing it for better results, as seen in the UE documentation below:
Adjusting Reflection Probe Resolution
You can globally adjust the resolution of the HDRI Cubemaps that are used for the Reflection Capture Actors by doing the following:
- Open up your Project settings by going to the Main Toolbar and then selecting Edit > Project Settings
- From the Project Settings menu go to the Engine > Rendering section and then look for the Reflections option. By adjusting the Reflection Capture Resolution option you can increase or decrease the size of the HDRI Cubemap Texture that was specified.
Please note that the Cubemap Resolution will only work with numbers that are powers of 2 like 16, 64, 128, 256, 512, and 1024. When using values other than a power of 2, it will be rounded to the nearest accepted resolution value. Also, be extremely careful when using high resolution values as it will dramatically affect performance due to the GPU memory requirements.
As for further adjustments with Lumen, the guide below helped me a lot on my own projects, when dealing with metal and glass:
