Round table

Recently, during a stream (unfortunately, I don't remember which one), I saw something inexplicable: neutral units that were previously eager to join after the hero's army increased in size – started fleeing! There was no change in the status of the most numerous stack of the same type of units (which affects joining) or any other effect described in the game mechanics. It was checked with the "See" spell, and the hero had enough gold. Can anyone diagnose the issue from the screenshot?)