I have also been having this problem I am only able to do one battle before the bug begins and I have to close and reload the game. I have the core DEI mods installed and then 2 Rome legion cosmetic mods and the no secession mod for DEI.

This has been annoying the hell out of me! thought id done something to mess it up but i guess it is happening to others.

Looked it up on reddit (also works for me since I had the same issue) and what you have to do Is: Open task manager when the game is launched (has to be in the main menu screen) - go to "details" - right click on Rome2totalwar.exe - click on affinity - open ups a tab where you have to deactivate set n. Of cores based on how many you have I.E I have 11 I only have to deactivate 3-click OK after you have deactivated atleast 2-3 cores based on how may you have - enjoy. If you didn't understand much of what I said I can just link you the reddit link lemme know! Sadly you need to do these steps all the times after launching the game however it stays on for the entirety on the game launched untill closed.

it's because of windows update 24h2.

getting this bug myself

same. mod is unplayable.