I also ran out of fuel round 20 miles before midway after a very succesfull patrol. I was so frustrated (didn't save the game) that i decided to sink my boat and end my career by that way

. While doing that i noticed that i was moving

! So i stabilized my boat... After a while and a lot of time compression i reached Midway!!!! I was only able to travell while submerged, so i had to watch the CO2-level carefully.
I guess this was a bug, but i reasoned for myself that "as an experienced skipper" i utilized the North Pasific current (actually flowing that direction) to reach my destination, though i was able to travel the plotted course...