MMH5.5 - Heroes of Might and Magic 5.5

The campaign in the mod is unplayable. It's one thing when heroes sometimes don't move because the scripts aren't working. But sometimes the enemy heroes kill the necessary creatures on the map, without which the mission cannot be completed! For example, in the first mission of the second campaign of The Restoration of Erathia, where you need to kill two stacks of dragons. You'll kill the first one, but then the enemy hero will kill the second one, and that's it. The mission cannot be completed after that.
Moreover, some heroes have lost their unique abilities. Arantir, for example, can no longer summon the avatar of death. I suspect that other heroes have also lost their unique abilities.