Hero Splitting

I noticed the topic and decided to write. Over 5-6 years of playing on different versions (although I only started playing seriously in the last year, before that it was just casual), the duplication happened periodically, but not often. Both on 3.57, 3.85, and Platinum 4.0, whether playing on a physical network or through Hamachi. It happened more often to my friend, who is my regular partner. We recently played a game, and it happened to me, but I took advantage of it; the game didn't crash: the duplicate stood motionless on the road in the dungeon, while the real one (he was a Necromancer) ran around, and the troops I transferred to the duplicate ended up with the real one – no spell can compare to that. I'll rummage through my mess of save files; maybe I'll find it. Or it's a bug, or it's an undocumented execution of some condition. These are the kinds of wonders that, unfortunately, are uncontrollable.
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P.S. The only observation: most of the duplications occur mainly with the blue player.