Thanks a lot for reporting the bug, including the repro-steps, Selentic! I guess this bug has gone unreported for so long because it has hidden by the auto-panning camera. It seems the cause of the issue is that the tick event in ATBTT_PlayerController fires after a new unit is activated, but before pathfinding is done calculating, which is done over a couple of ticks by default when using Find All Possible Visible Tiles. Finding the reason for the bug was difficult, but solving it is very easy. In the Begin Unit Turn comment box in ATBTT_PlayerController move the node setting Current Tile Hover to -1 from at the very start of Activate Unit to the very end (at the far right, after Disable Player Controller Input is set to false):
Though it will occur frequently in most games, this is a very serious bug, so I’m sending a hotfix to Epic immediately. Thanks again!