With Zeldor it is likely due to karma. Evil follows evil they say.
Seriously, I do know we had battle replay bugs in Fallacy and there were virtually no mods used in that game at all. velusion hosted it at the start and he is not a big mod guy.
Manatee also had battle replay bugs and it used no mods at all. I did not play in that game, but i noticed there were posts in the thread about battle replay issues and I took notice of them since we were having them in Fallacy.
In Fallacy they were not game determinative. And there were not many of them. I think there were 2 or 3 and they were between myself and Reay mostly. Not sure any other nations reported the bug and it was a 22 player game that went 108 turns. So that is a lot of turns and a lot of battles to only have a handful of replay bug errors.
That said, the goal is obviously to eliminate bugs completely.
One thing I do know, the battle replay bug is not caused by mods. Whether mods make it worse, who knows? But it exists independently of mods.