garageCube

Playing around with the beta and noticed a difference in how 3.7 and 4.0 handle the Silhouette Luma/Alpha blend mode. I has a source from a 3rd party app that I use as a mask with the Silhouette Luma or Silhouette Alpha Blend mode. In 3.7 it blocks the image below except where there is input from the program. In 4.0 it just layers it over with a ghost layer.

I'm rather ignorant in exactly what is happening here but the behavior is pretty different from 3.7 and 4.0

We solved a lot of issues with the combination of blend modes / surface opacity / media alpha in MadMapper 4.0. In 3.7.5, if you chose "Stencil Luma" the opacity was ignored. That is now solved. I suppose that's your problem.
If it's not, just send a minimal project file (together with the images in a ZIP) we'll have a look. But I just checked again and it does what it should.
Are you using an FX ?