Hello,
4.19.0 for some reason is resetting all material instance parameter values to default. It’s not limited to our projects. Some others also reported this. I’m going to file a report today about that. The quick fix is to just see what the parameter values are in 4.18 and enter same values in 4.19 again. We have a ton of content on marketplace atm and it would take a long time to do this for all our content and submit updates, I’m rather trying to find out of Epic is going to address this issue in the hotfix.