=media-libs/openexr-3.1.4-r1 is slotted as openexr:0 when it should be slotted as openexr:3
No, it's specifically being unslotted, due to the huge number of bugs. See bug 833158. Please file a new bug with specific issues you're hitting, but make sure you've emerge --sync'd first, and you don't have any stale package.accept_keywords entries for Blender and friends first (not that it should matter much now).