I've got 3 x Phantom Knights & Priestesses of Chaos plus 2 x Dark Adepts all weakened to one on my manor. Unfortunately, none of my friends can see them and nor can I see theirs. Sadly, this also appears to affect Chan the Topless Florist too which is a terrible shame.
Maybe after a full day (and remember GI work to more than 24 hour cycles ), it will sort itself but I fear that they have fixed this. I suppose it was a good glitch while it lasted.