Ok Shadow Templar just finished some test by launching all three bretonnian campaigns.

For the test I opened by task manager and followed the "Warhammer 2" task during the whole process. During the launch on a campaign the Warhammer task was marked several times as "not responding" but the hard drive keeps working and the music/soundeffects are playing the whole loading process - and finally the campaign was loaded and I was able to play.

Test enviorment:
Active mods: HKO - Units and HKO - Lords
Launcher: vanilla game launcher

Conclusion:
After the tests I came to the result that my mod/s taken by themselves maybe leads to let the game be shown by the task manager several times as "not responding" but keeps working and dont lead to a crash.

I will try to help you figure out what the problem is and if it has to do with the combiantion of other mods and mine.

For a beginning please try to start the game/campaign with the vanilla game - so no mods activated. If that works (it should work) then try the same with my mod activated. As I mentioned it might take a while till the campaign is loaded but that should work aswell.

Thank you very much for the time and effort you put into this! I will start a new vanilla game as soon as possible.

I started a vanilla game and it worked just fine.

I forgot to mention some important details regarding the crashes:

I was using other mods in addition to this one. All of the mods were working just fine until one day, the game kept crashing every time I tried to continue campaign. I could still play a vanilla game, but I couldn't play a modded one.

Yesterday, after a while of research and pondering, I concluded that my computer (MacOS version 10.14) was too outdated to run a modded game. So I updated it to MacOS Catalina 10.15.

After the update, I started a new campaign using the same mods. Everything went fine. The mods were working and there were no crashing. After I short break, I tried to continue the campaign, but the game started crashing again.

(On a side note, your units still appear in the Bretonnian roster for Custom Battle.)

I hope this information was helpful.

Well savegames often stop working after an system update.
If I got you right then all mods are working fine now my one inclusive, right?

As of now, the game keeps crashing whenever I try to continue the modded campaign. (I'm using multiple mods, including this one.) I will try to start a new campaign with aforesaid mods and see if it crashes.

It crashed. I tried to start a new campaign with your mods only (Holy Knightly Order Units and Holy Knightly Order Lords). That didn't work either. In fact, I tried starting a new campaign with other mods, but the problem still persists. I can only play vanilla campaigns.

I don't think this mod is the problem. I think it's something else. What say you?

You are right. If my mods were/are the problem then other activated mods should not lead to a crash.
Im sorry but I really dont't now how this compatibility-thing works with MacOS.
Maybe it is an option for you to use this one: https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=1399787504

This is a custom mod manager - because the vanilla launcher seems to be buggy when it comes to multiple mods.
I hope that is the solution...

I downloaded the mod manager, but it didn't work. It said that the application can't be opened "because Microsoft Windows applications are not supported on macOS."

I guess the only solution is to switch to a PC. Thanks for your help.

I'm sad to read this but we found out that all mods especially my ones are working correct.
There might be workarounds for such a - I guess- macos compatibility issue.
In this case I'm sorry that my help leads not to a success.

Maybe the latest update will solve you problem. It seems that the savegame crash was a common issue and was/is adressed in the new patch.
Patch notes:
https://www.totalwar.com/blog/total-war-warhammer-ii-patch/?fbclid=IwAR2r3i0n_BsStQF2_xMvhNk8bH0ED0M3NmjaKd9Kr2xYE4V_Yl-C3OGZf6k