This is my solution for my situation, I have a character customization system that changes face and body shapes, as usual the flickering is intense and disgusting.
What I noticed about the flickering is that only the vertexes affected in the most recently modified morph targets flicker. So to solve it I made a morph target that has virtually no changes (just a single vertex that moves a fraction of a unit) I named it fix_flickering and made a blueprint that sets it to a random value between 0.2 - 1.0, so everytime I change the value on other morph targets there’s a 0.1 second delay and then the fix_flickering morph target is set to a new value and that gets rid of the flickering on the previously affected areas.
Note that this work around does not work if
1: The delay is less than 0.1
2: The value in the the morph target that fixes the flickering is used twice in a roll (this is why I have made it a random float).
I doubt if this will work well for talking animations but if you are simply trying to change a character facial or body appearance its good enough.
