Background: Denmark inherited both Norway and Sweden, then Norway broke free and is now a 1PM in Shetland. I, Great Britain, have diplo-vassalised them.
Now: I was going to annex Norway, but then I saw that Denmark was being torn apart by rebels - specifically patriot rebels - so I thought I might as well wait for Norway to get a few provinces before annexing them. Sweden broke free, Holstein broke free, but the Norwegian Patriot occupied provinces don't. The rebels at one point controlled all of Norway's cores, but, one-by-one Denmark re-took them. Or so I thought. What was actually happening was that the provinces occupied by Norwegian patriots were defecting to Denmark. I looked a bit closer at the provinces and over the shield for the Norwegian core the tooltip said that the core was supposed to have disappeared by 1552. And it's now the mid 17th century.
What exactly is happening here?