Thanks for your feedback. Back at the beginning of the Game Jam, I was testing making the ants move 2-3 times faster than they do in game now, and would occasionally see ant moving back & forth but they wouldn't attach leaves to the branch. This would only happen of very high speeds, so that's why I capped the ants speed to what it is now. Basically Unity's pathfinding would struggle at high speeds when the frame rate dropped too low. I haven't been able to replicate that issue in over a week though.
The fact the error was happening on the 3rd tree suggests ants were near their top speed? Is that correct?