I have been getting some weird pathfinding bugs with builders. This is with unmodded Gathering Storm. It's been a long game (World is in Atomic Era). I have lots of railroads and in areas with lots of other civilian units, the game's pathfinding gives me lots of bad paths for my builders. Somewhere 7 or 8 tiles away that I should be able to reach in one turn, instead the game has me take a circuitous route that takes 2 or 3 turns. The game is especially bad at pathfinding with embarked units. When you can move 8 or 9 tiles by water, the game logic seems to prefer taking 2 or 3 turns by disembarking and then re-embarking.