Round table

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