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Hey, sorry to necro an old post, here 1.5 years later I get this bug often. I can usually fix it by holding alt and following, then clicking again, but it comes back often. It can be frustrating, like right now, i didnt have enough wages to pay my men, and i was completely unable to attack the enemy(until i figured out the above method, but it was a little too late haha)
Edit: Just had a similar bug that might be related? For some reason, my party wasn't following, but was matching the speed of the enemy. Again, the fix was to alt+click, then click.