Steve, I've hit another LP routing bug (or the same bug again). I sent some cargo ships to deliver mines to a colony in the system next door, and it decided to take a very long path to LP2, which is near a planet orbiting the second star in the system, in order to get to LP1, which is near a planet orbiting the primary. The fleet ran out of fuel about half way there, a mere 10 billion km or so short of LP2. LP1 is a Lagrange point that I stabilized myself specifically so that I could get access to the secondary, but ships have gone to and from the colony around the primary a number of times since then; this is the first time any have tried to go the long way. Since it doesn't happen every time, I suspect that reproducing this will not be straight forward.
The image shows the orders and the tactical map, so you can see just how long the route is. In particular, I note that the "All Orders Distance" shown in the movement orders is only 4.02 billion km, which is a good estimate for how long the route is supposed to be.

Sadly I'm still using 1.73. You haven't mentioned fixing any pathfinding bugs in 1.80, so I hope this bug report is still useful to you.