HoMM3 HD is a mod (add-on) for the game Heroes of Might and Magic 3.

I mentioned before about the free units given out in refugee camps and when buying from the castle's shop (+1 air unit), but the author ignored it. And the bugs are 100% due to mods.

Please provide detailed instructions on what needs to be done to trigger the bug.

I'm addressing everyone. If you are interested in fixing bugs, please write detailed recipes (sequences of actions) so that I can reproduce the bug. General statements like "there is a very, very bad bug" are of no use.
If the bug does not occur consistently with the same sequence of actions, it is extremely difficult to fix. However, the more detailed the description of the situation in which it occurs, and what preceded it, the better.