Well, but with 99,9 % certainty, it can't have to do with the submod changes, as i described formerly: All of Gondor's units are save to function properly. And Mordor's units are the same as in TATW vanilla (there are only a few stat changes done). I'm afraid i can't help there.
All right. It is quite possible that some nasty mistake sneaked into 5.7 (while it was ok in 5.6) and that it has nothing to do with your mod. I am still hesitant to forward this discussion to Germanicu5, because at this moment you are waiting for his reply on his thread.
Btw, G5 has great experience with incompatibility of different mod files with his own and usually helps modders very much to discern which battle CTD belongs where. If he has time, he will gladly help you and will help you in details.
Edit: I dl'ed/watched the log, but can't find an indicator, and i have no time for a further detailled bughunt. For now, i can only recommend to play this submod, as it is offered with the install instructions of the 1st post, that is then just without the G5 BAI update 5.7.
Please describe also exactly what happens (is it a battle loading ctd or in-battle?, at which moment the game crashes?).
It is battle loading ctd. Battle cannot even start.
For a check (just comes to my mind), you can try the mentioned nazgul unit in custom battle, if the unit makes anger, but that would mean they make issues also in TATW vanilla
There were no any reproducible CTDs in vanilla TATW with nazguls or any Mordor units/battles during first 100 turns, but with 5.6. I didn't test vanilla TATW with 5.7. You need to pay me in real money to do that, because I am a "little" saturated with vanilla.
(i don't know what you mean with "southern nazgul", if you mention units, please use the exact in-game name).
This you would understand if you looked save file, because there was another nazgul in save file with another possible battle on the north. (I am not criticizing you, and am not insisting that you look into save file. I am just saying as information) So, that "southern nazgul" is now completely irrelevant.
And please also mention the turn when the crash occurs, so i can get an instant idea where you are in your campaign (campaign-flow ... recruitment).
The turn is 13 and same or close turn number was when that CTD happened in first game. The battle is offensive and I am aggressor vs Gondor (in both games). In first game there was 1vs1 stack (Mordor/Gondor). In 2nd game there is 2vs1 stack (Mordor vs Gondor) or 1vs1, CTD is happening anyway (You can choose to replay battle without 2nd help attack stack by choosing "night battle", because 2nd helping stack does not have general) The number of units in all stacks is relatively small so it can't be memory issue. (For memory leak I need to have 5 or 6 stacks on battlefield on huge scale late game and this was large scale at beginning of game)