Hey ,
So I ran some tests and found some helpful information that you can use and apply to your own set up. So the ‘bug’ you referenced is actually not a bug, but how SSR is calculated when used with FXAA compared to Temporal AA. We know about this limitation, and there is not much focus on FXAA, so addressing the limitation and solving it is not the highest priority.
With that said, because translucency happens in its own pass, if you use a translucent material blend mode with your World widget UI, you can get a clean reflection when used in conjunction with Temporal AA.
Below are the comparisons between a ‘Masked’ blend mode and ‘Translucent’ blend mode. You mention you are using the SSR option checked in the material. However, I am not able to render the material as a widget in the World or the Screen unless the ‘Material Domain’ is set to ‘User Interface.’ As soon as I do this, the options for SSR are no longer there.
Material Domain ‘User Interface’
Transparent ‘Blend Mode’ in Blueprint
Transparent SSR
As you can see this is much cleaner than the masked screenspace reflections as seen below.
Masked SSR
As you can see, Temporal AA really does not like masked materials when used with SSR. I would stick with either Opaque or Transparent blend modes when render widgets in the World with UI.
If you have further questions, please send some screenshots of your specific set up so I can take a further look. What you have encountered is essentially a limitation of Temporal AA with Masked materials and the reflective environment. This is something we are aware of, but there is not a lot of focus on improving this limitation at the moment.
Cheers,