Encounter indicators disappearing

[michelcolman]

I sometimes have a hard time planning an encounter with an object, because the encounter indicators often disappear for no reason, showing a different (and often less optimal) encounter somewhere else instead. For example the day before yesterday, I was doing the first asteroid redirection tutorial and trying to zero in on an encounter at the second intersection with the asteroid orbit (with a fresh maneuver node, not the given one). When I tried to optimize that encounter, it turned out to be impossible to achieve. I kept getting closer, 2 km, 1.5 km, 1.2 km, and then with a tiny extra tweak which I was hoping would get me to within 1 km, the encounter indicator disappeared and jumped to the first intersection instead, with a distance of more than 10 km there. I did not accidentally make a big correction, because a tiny tweak in the other direction brought back the first encounter, but I could never properly line up that one. It kept disappearing so I couldn't get it close enough.

Even worse was when I was doing it with maxConics set to 7. The planned orbit went through the asteroid orbit twice (two possible encounters), and then passed by Mun into a new purple orbit which went by the asteroid again. When I was trying to zero in on an encounter on the first orbit (getting close to 1 km), the encounter indicators suddenly jumped to the purple line way in the future! It was impossible to line up an encounter on the first orbit. 

In the first case I thought a perturbation by the asteroid on the first passage might be to blame (although it shouldn't, since it has no gravity at all), but in the second case that's totally impossible as it prefered to show an encounter on the second, purple orbit rather than the much closer one in the immediate future.

Is there any logical explanation for this behaviour, or is it just a bug?

(I know, I'll give MechJeb a try, but for the moment I just want to get the hang of stock KSP before spoiling myself with automatically calculated trajectories)

By the way, another bug that often happens (and I seem to remember being discussed on the forums as well), is when sometimes it's impossible to add a maneuver node to the blue line and you can only add one to the purple line years in the future. Sometimes you can still find a spot on the blue line that accepts a click (close to the periapsis often works, but not always) and then drag it to the spot you want. But quite often even that doesn't work. I hope that will be fixed in the next version?

Thanks,

Michel