I see what you mean on the video, I don't think this is new in our latest preview, this often occurs in very low light conditions and once I stop moving the image looks good.
I was still not able to reproduce the light issue with IES files either, does the effect improve if the walls are thicker, or are they already?
Additionally, for us to further test this, could you perhaps share a small test project with me through something like WeTransfer?
If so, you can share the link with me through a DM, please also send in a feedback report via the Enscape Feedback Button and include a link to this thread and my name in the description
1st image is 3.1
2nd is 3.2
3rd is the representation of the ies file in Revit.
It looks to me like 3.2 is using a hemispherical light shape and not the ies file.
and below is a link to the Revit file used.