Update material instance parameters in level viewport only works on mouse-up

I have a simple material setup with an instance assigned to a landscape in a level. I want to adjust some of the material params and see the updates in the level as I click-and-drag the param to smoothly change the value. Only thing is the level viewport only updates on mouse-up. Any way to enable actual live updates of material instance params in a level viewport?

This has been going on since about 4.24, I don’t think there is a solution, I’m afraid…

EDIT: I just had a quick look, I can’t find other people reporting it, but have defintely seen it ( and experience it ).