I stumbled onto a rarely-occurring bug that has noticeable impact I started this game at SVN level 11430 (V42.0.BETA.6724), and have not yet updated. I suspect it may have appeared well before this SVN level because it seems to only be triggered in 1% or 2% of newly-generated games that specifically include 1 or 2 randomly-selected AIs. I did not notice this bug until several hundred turns later when using the WB "player" capability to view and compare counts of resources and troops using the WB "player" function's pull-down list of the to select the player or any AI. When I opened this pull-down list I noticed something very strange and wrong. There were 2 entries for the same leader (Wu of China), both flagged with a red background. I then used WB to scan the complete map, and found 2 widely-separated settlement areas both belonging to Wu.
More information and/or guesses that may help locate and fix this bug, plus suggestions for players on how to minimize the chance of this bug occurring in their game
(1) I suspect this bug occurs only at game start-up and map generation, with a very low probability that a randomly-selected AI will be assigned the same civilization name as an already-named player or AI.
(2) I'm guessing the odds of this bug causing an issue in game generation is about 1 or 2 in a hundred (assuming each randomly-generated AI has about a 1% chance of picking the same civilization as the player or any specified AI or any previously-generated randomly-selected AI ( all in the same list of about 100 civilizations).
Suggestions to avoid this bug until the fix is completed:
1) Do not specify generating any randomly-selected AIs (unless you really really want them, and are willing to use the WB fix-ups described above to detect and erase all cities belonging to one of the two same-leader civilizations).
2) If you have just started a game and not yet played more than about 100 turns, I suggest using WB as above to check for duplicate civilizations. If there are, I suggest starting a new game (unless you really really love this map and are prepared to use WB to find and delete one of the duplicate civilizations. There will probably be some negotiation in a multi-player game with players close to or far from the now-available erased AI's settlement area) .
3) If you are several hundred turns into the game already (like me), want to continue this game, and are willing to use WB to find and erase all settled cities of one of the duplicates, then keep playing. An unexpected bonus is that that some players may may move up on the scoreboard because the scoreboard trustingly summed the impacts of the two same-name civilizations (which will stop happening immediately when the fix is made, or you use WB to erase one of them). This will definitely require a lot of negotiation in a multi-player game.
(2) I'm guessing the odds of this bug impacting game play during new game generation is only about 1 in 100, multiplied by the number of randomly-assigned AIs. This guess is based on the odds that each randomly-generated AI has about a 1% chance of picking the same civilization and leader as the specified player and all the specified AI and all of the randomly-selected AIs ( form a list of slightly over 100 civilizations).
(3) Theoretically this could happen in any game, if the game start-up options screen does not ensure that the player and all specified AIs have different civilization names. I don't this can occur.
Suggestions for other players to avoid this bug:
1) Do not generate any randomly-selected AIs (unless you really really want them, and are willing to use the WB fix-ups described above to detect this case and possibly to erase all cities belonging to one of the two same-leader civilizations (will probably require negotiation in a multi-player game).
2) If you recently started a new game and have not yet played more than about 100 turns, I suggest using WB as above to check for duplicate civilizations. If there are, I suggest starting a new game (unless you really really love this map). It is probably faster and easier than using WB to fix it. This approach will almost certainly require negotiation in a multi-player game.
3) If you are several hundred turns into the game already (like me) and want to continue, and are willing to use WB to find and erase all settled cities of one of the duplicates, then keep playing. An unexpected bonus is that that some real players and AIs will move up on the scoreboard because previously the scoreboard added the impacts of the two same-name civilizations - which will stop happening immediately if you use WB to erase one of them, or start a new game after the fix is implemented). This will definitely require a lot of negotiation in a multi-player game.