Heroes of Might and Magic III - Complete Collection + Era2 + VCMI + Utility.

I understand that you are playing the VCMI version. These heroes have been in development for a long time, but its version has not even reached 1.0 (the current version is 0.99), so there may still be many bugs and shortcomings (although there is already a lot of content modded for VCMI). I added it to my VCMI build relatively recently, based on the principle of "why not." Most likely, many errors will be fixed in the near future.

Yes, I know. I was even surprised that in your build, all the cities loaded well and you could play them completely (even the Asian Amethyst). In September, when I tried playing VCMI (it wasn't your build, but I just downloaded the VCMI client that was current at the time), it was a terrible ordeal with bugs, and it was generally impossible to play, except to put together a specific set of mods (new castles) and just test the castles themselves, and even then, not for long. Now (most likely due to the release of the new VCMI version 0.99), you can play quite normally, albeit with some caveats.

P.S. I wonder if crashes with portals also occur if you play the original VCMI without connected mods?

I don't know, I haven't tried it yet.

P.S.: I found these castles on the internet (which are not in the build):