Problem: when a vassal capitulates AND gives a city, the Land statistics vs Original for the vassal (and probably the population %) are calculated as it is BEFORE the agreement, and not AFTER the agreement. If the vassal gives away a city when capitulating, statistics will be immediately reduced, and, instead of starting the Vassal Agreement with [Land: 100% of Original], it will be immediately lower!!!
Side effect: If a vassal gives away SEVERAL cities, or cities with large radius, then right after capitulating he can even be free again as the statistics can reach less than 50% of Original land!!!
Case: scenario "Chinese...", as soon as Chu Mi Lu capitulates, the statistics are [Land: 80% of Original] instead of starting at 100%.
1st pic shows the diplomacy screen before capitulation: I ask for the city of Sakae.
warlord-Chinese scenario-before Chu capitulation-muBC.jpg
2nd pic: capitulation and city accepted: I immediately check the stats, and it shows that the Original land is already reduced.
warlord-Chinese scenario-after Chu capitulation-land at 80%-296BC.jpg
Replicating the problem: with the saved game attached, attack and take the city of Yiang, contact Chu and ask for capitulation AND city of Sakae. after his capitulation, check Mu's stats.