[Not a Bug] Maneuver nodes are not stable when burning several orbits in advance.
When you plot a maneuver node and you execute it, markers are somewhat stable in the navball. The remaining deltav is reliable and decreases over time until the burn is complete.
Suppose you have a ship with a low TWR (ion engines for instance) and you have a very long burn ahead. You will have to make several burns in advance to slowly raise your apoapsis and gain benefit from the Oberth effet. And here comes the bug: if you burn at least one orbit before the actual maneuver node behaves erratically.
- The maneuver marker start bouncing everywhere (the earlier the burn, the more it bounces)
- The remaining deltav
To reproduce the bug
I have made a short video to show how to do the same.
The game is absolutely stock + the 2 DLCs (fresh installation to be sure).