1. There is such a bug, when a computer attacks your castle, you escape from it, then the computer not only does not capture the castle, but it also ends its turn.
2. I would generally prohibit any escape from the city and introduce ransom instead of it, especially since the skill of diplomacy would be useful.
3. When the computer escapes from the battlefield (which happens quite often), all its escaped heroes crowd on the same square in front of the city and, as a result, get stuck there.
4. Another question is whether creatures from external dwellings can themselves be in the castle (already purchased, or available for purchase). It is simply inconvenient to take 5-6 dwellings with neutral to the nearest town and collect them in a heap. Thank.
5. The game often crashes when loading saves. Sometimes they are completely constipated. They break in 100% of cases if you close the frozen game through the task manager.
6. Problem with Necromancy and Demonology (summoning skeletons and demons for mana after the battle). The problem is that it costs mana to summon. Just one call of a pair of besiks or skeletons and a hero with his specialization is completely useless, plus he is left without mana for the duration of the battle. Summoner in general IMBA is another matter.
7. Can you somehow speed up the game itself 2-3 times? So that the heroes quickly ran around the map, and there was an auto battle to choose from and the computer's move did not have to wait a couple of minutes. And in general, a lot of good chips can be stolen from Heroes 3.