Go to Western Seas with a lv6+ ship, make a path that crosses all the most shallow waters you can find, and on the 64th tile, you won't be able to drag the path further, or reduce it at all. You can switch to Eastern Seas and back to Western Seas, and it'll work again, but there seems to be an invisible limit of 63 tiles before it bugs out.
I have this same issue. I have the ship fully upgraded, but I can't go the full distance. It's frustrating that I can't use my ships full potential.
You can use the whole distance if you don't cross a bunch of shallow squares and sail across deeper waters instead, which is probably what they were designing it around (most of Eastern seas is much deeper than Western seas). I do like sailing across a whole bunch of really shallow waters though, since it gets easy gems :c
It was the 64th bug. Unfortunately midoki has a limit of 63 bugs, anything beyond that gets stuck in limbo.
If all goes well, are you hoping to have an intermediate bugfix before any sort of winter content update? Or are we looking forward to a larger, but more exciting winter festivity?
I have an idea as well. 99% it will happen just after i started a 6 day lv 12 upgrade of my grog facilities, with all of my builders busy.