We recently switched to 4.15 (from 4.14) and have found that imported (or re-imported) LOD meshes don’t display. Auto-generated LOD meshes display fine, but when we try to use our own LOD meshes they appear to be invisible. No errors are given when importing the LOD meshes.
They simply don’t display when we get to the proper screen-space size. It should be noted that older assets which were setup a couple of weeks ago still correctly display LOD meshes (which were imported at that time).