I keep having problems with patched conics, where after my maneuver it says for instance at Duna I should arrive about 200km off, but when i get about halfway between the transfer (No RCS or accidental engine touches) the patched conic suddenly changes to another number, however once I get to the planet it is a whole other number that isn't even close, in one of my games it got about a million km difference. Is it normal for it to be like this, and is there a way to minimize or hopefully fix this problem? The game version is 1.8.1.