SpaceSimCentral

I have been trying to report this bug for many years now, but there has been no way to go on the other forum at all. I go on again to check and see this forum has been added.
The bug is as follows; when using the autopilot for long journeys it will accelerate until it runs out of fuel leaving you dry and stranded. This is highly game breaking as it not only affects the player but every NPC uses the autopilot for their navigation, so every NPC will eventually get stranded leaving the game empty and barren with no NPC encounters.
As I can tell this bug was introduced sometime after the november 2016 build of the game, which does not have the bug, and never fixed, or noticed. very low standard of development and very low community engagement. Sad.

What do you call "long journeys", please ?

The autopilot is simple; it accelerates until it is time to slow down so that the ship touches down precisely on its target. It does not calculate whether your ship has enough fuel for the journey - that is your job. There are routes you can leave to the autopilot and go to sleep. And there are routes that you should plan yourself, because the fuel costs alone (manual versus autopilot) are way out of proportion.
For me, this is not a bug but a way of ensuring that Pioneer does not degenerate into the 'Autopilot Simulator 2021'. But as 'Cpt. Blood' already points out, maybe I'm underestimating what you mean.

The simplest workaround is to target the parent body of your destination, and only switch to your actual destination when you are quite close.
Bodies on a tight orbit tend to go around quite fast, and the autopilot will constantly compensates for it, burning quite a lot of fuel in the process, because the maneuvering thrusters are less efficient.
Also, manual flight is also feasible, and can be challenging and fun. The UI is there for it, right around the reticule. Left gauge is the deltaV reserve, if the gray line is above the white, then you won't be able to stop. On the right is the stopping distance indicator. Fill it up to almost 100%, flip and start braking with your main engines. And don't forget that when accelerating, you are "pulling" your prograde marker towards the crosshair, and while decelerating, you are pushing it away. With these behaviors, you can pretty much control your path without ever using RCS thrusters, you just need to aim off appropriatelly.