Same here, 4.12.5 - started happening today for a reason I do not understand yet.
Things I noticed: It happens for child blueprints of a base blueprint class. Only properties are affected that are inherited. The moment I set these values to “none” in the parent class and specify them in the child instead, they “stick” after a restart. Workaround - but not nice.
These child blueprints are in a folder. I cannot verify this 100%, but it seems to affect the first blueprint in the folder, not the second any other after that. I tested it by renaming them (switching order) and it started affecting the “new” first child blueprint.
It started happening after I cleaned the project up a bit. I have 2 skeletal meshes and pawns I use in game and a base SK mesh and pawn that I had around because it came from a sample project. I cleaned the two base versions up, including the skeleton they had and replaced the now missing references in the animation blueprint with one of the 2 skeletal meshes I actually use. Once I restarted the editor, I noticed that this behavior started