This is an issue I have encountered as of yesterday. Sections of geometry from walls, individual objects such as stairs and folds of blinds over the windows, panes of glass, and decorations are having sections of polygons taking materials from other objects and applying them to their UVs. I have imported it in a number of ways. OBJ, FBX, both all as one object and also as separate pieces. I am planning to make all of one type of object one object in itself and then importing it like that to see if it will prevent the material IDs from crossing object types…can anyone shed some light on why it is Unreal Editor is confusing the materials like this? Really would love to understand why this has started happening or what I am doing wrong. Thank you.