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

Regarding the case with the level 30 hero in prison with weak guards – I can't imagine how HD could be involved.

I suspect that the reason is the fix for starting heroes that are not level 1.

How the fix works: it simply removes starting heroes from the list that the game uses to place a hero in the prison. That is, when the game gets to the point of placing a hero in the prison, the random generator never generates a starting hero. And an empty prison will only appear if all heroes have been used up. So, the fix doesn't work like in WotG, where a hero already placed in the prison is removed, leaving it empty. The fix doesn't affect the hero's level or the prison's guard strength. Therefore, I'm also not inclined to link the message about two empty prisons in a row to this fix. However, I am not the author of the fix. We will investigate.

Added 4 minutes later

I play on streams myself, and most of the opponents are on it; there was one crash, but there wasn't time for crash reports; if it happens again, I'll write.

Well, if there was a crash report from HD, the information is saved in HD_CRASH_LOG.TXT in the game folder. We need that file.