#126 seems to be present again in mod ver 8.0 on 1.21.4 at least. Issue appears when Fade effect is enabled and the vanilla blur effect is applied. Disabling the fade effect corrects this issue.

Excuse the overexposure in the video, screen snip doesn't convert HDR well.

In my other modded instance the entire screen becomes black where the blur should be applied:

Here is it without the fade effect. I'm using the Blur+ mod to blur inventory screens:

This bug will be the end of me. I spent weeks already trying to understand it. For now I will focus on other areas, so no promises as to when I can find a solution. :(

At least, the latest version (8.1) makes Move mode work again if Fade mode is disabled; that should hopefully circumvent this bug. Though I have not extensively tested this.