Leoreth I went back and played the same game from an earlier save, this time without worlding anything. The most I did was looking at the map. No religious tweaking this time.
The game played out slightly differently than last time. I didn't take make peace with Rome or Greece, so the wars with Rome and Greece continued much longer this time. For some reason this allowed Rome and Greece to last longer, but they still collapsed by the 8th century. I got a gem event in Australia, and still gave my core cities to Rome before the Arabian spawn so I wouldn't get hit too hard by the flip.
Anyways nearly the exact same thing happened, but on a different date. Ethiopia (which has been dead for hundreds of turns) converted to Orthodoxy, and Orthodoxy popped up in the Norse cities. Greece, which converted last time despite being dead, did not convert this time. The ERE still didn't spawn, I believe because Rome never conquered Byzantium. The AP hasn't been built yet--I intend to build it soon.
So it seems what I did in my last game didn't really matter. The bug was reproduced anyways.
I uploaded a save right before and right after this happens. I use the latest SVN.
Spoiler :![]()
What exactly is the bug? Orthodoxy sometimes is autofounded at Kiev's spawn (or if Russia gets orthodox missionaries earlier) and orthodox civs convert to orthodoxy no matter dead or alive. All these are intented, I think there is no bug here.