I'm not sure if this one is a bug, or if I'm misunderstanding the UI. A neighbor declared war on me and shortly thereafter took the only territory I had claimed besides my capital's territory. When viewing progress towards era stars it said I owned 2/5 territories necessary to achieve a star, but the only territory I owned was my capital's territory.

Reproducibility 1/5

This one is very situational. If I can find the save where it took place then I'll try to provide it here.

Edit: It was too long ago, the auto-save no longer exists.