My Yi Ti game has run into an annoying problem. It seems that when I go to war, some of my vassals, just as they should, temporarily become independent due to the megawar system. However, once the war ended and I got the "the wars have subsided" event, not all of my vassals joined me. It's now been about 1.5 years since the war ended. They won't accept an offer of vassalisation.
Seems sort of broken to me. Is this a known problem?

Seems sort of broken to me. Is this a known problem?