This issue has existed for a number of versions now… but I thought to report it anyhow.
When using the FBX importer (file->Import into level, not the one in the content browser), UE creates the content, but rotates the materials on only the last of the instances in the level. So when I import, let’s say, 10 chairs with wood and fabric, on 1 of the chairs the wood and the fabric will be reversed.
It is possible (but I don’t think it’s the case) that the mixup is caused by Blender (the tool from which I’m exporting).