Decadence error?

[Yorck]

Playing the 550 BC scenario as Lydia, which already favours the Persians fairly heavily. However, I am wondering if I am now seeing a bug. Persia went through some sort of convulsion, usual nations breaking away, a couple of Usurpers formed. However, in the ~20 turns since, Persian Decadence is 1, producing a CDR of 3977. If I look at individual regions, it should be enormous (too many to get an accurate estimate, but the Mesopotamian regions alone total around 1000+. Every region I look at is in purple.

Is there some kind of temporary mechanism operating here? Or has the game file just become corrupted and therefore unplayable (Persia is getting free tokens and now crushing all of the breakaways)