I was working with material instances.
I needed to change the parameter name on the base material for a Texture2D paramater.
This caused all instances of the material to use the default base material’s texture instead of their texture that I set up.
This affected thumbnails and UMG widgets that I was working on for me. I didn’t have a chance to see what would happen in game.
I reopened each material instance and this caused the overridden texture for that instance to load in and update the thumbnails and UMG widget editors I had open.
Restarting the editor may help reset this as well but I didn’t have a chance to try.