Playing solo mostly, I almost always use tracks that assign my pitbox either the very first spot or the very last. Today I was futzing with Poznan, and found my pit assignment was about 2/3rd (.65.8889%) down the pit lane. While refreshing, I wonder WHY? Why are the bulk of tracks either 1st or last pit box and 'some' can assign my car elsewhere?
I had the issue in multiplayer - I did find it track specific though, some tracks it worked others it didn't. I changed the multiplayer.json file. Searching for the entry: "Assign Parking" If it is set to true, set it to false and try it out.
I think it would be related to how the pit stalls are laid out when building the AIW. So say the developer puts the first pit stall in the middle and then the second one is 3 spaces ahead and the third one is 3 spaces behind the first one. Fourth, Fifth, sixth, & seventh just fill in the remaining spots. The effect would be to give a 3-player game very open access to their pit stalls and up to a 5-player game would have reasonable access to their pit stalls, but a 6- or 7-player game would have tight pit access.