One is basically just limitations on the game engine (from what I've heard). You are unable to provide detailed taxi details to some planes, they read them back but do nothing more. You are then required to give them a simple taxi instruction and give them a new instruction once they've gotten part of the way.
For example, moving planes from the terminal where Joon and Airhop are located to Runway 08L. I need to give them "Runway 08L, taxi via R" once they reach taxiway R, I can instruct them further. If I give them the full instruction directly after pushback, they won't move, they won't load the planned taxiroute. I like to move planes to 08L through R, RN1 and Uniform.
There are some taxiways which just looks horrible. While the size and such are correct to IRL. In game it really did look like a graphical glitch to me when it zoomed in in actiona camera. So it is not an error, it is simply the amount of detail of some taxiways does not live up to the standard of details I was expecting.
(not the same taxiway circled, just noticed, but they are very similar in size and look both on the IRL airport and the one in game)