Appearantly when you drive slowly enough out of the yellow pitting box after the pitting has come to an end, it doesn't end that pit-state.
If you continue to drive slowly enough then you can drive to the end of the pit area, where, if you stop, it pits you again and when you continue, stepping a bit on the gas pedal, it spams with refueling message until you get a "BLANK OVERFLOW" and you get disconnected from the server.
In single player, it just spams that refueling message until you throttle up enough to get rid of that pitting state.

here are 2 videos of it (x264 mkv):
http://mikk36.eu/web/random_shit/lfs_pit_bug.mkv (15MB) - multiplayer full length
http://mikk36.eu/web/random_shit/lfs_pit_bug_2.mkv (1MB) - single player ending

i can confirm this.

it looks like that then:
STORE : OVERFLOW - ESTstreetr
Lost connection to ESTstreetr
Invalid (97) - could not find connection
Invalid (252) - could not find connection
Invalid (255) - could not find connection
Invalid (0) - could not find connection
Invalid (135) - could not find connection
Invalid (97) - could not find connection
Leave @ 56395 : ESTstreetr
ESTstreetr^L disconnected (Streetr)

Should be moved into bug section.

questions as follows:

is it a insim bug? (meaning the cruise app) >>>nope, tested, was in singleplayer mode!
is it a car bug? (reproduceable with any car) >>>nope, tested, LX4 used!
is it a track bug? (reproduceable on any track) >>> nope, on any track, Ky oval used as well
is it a Lfs bug? (reproduceable in singleplayer) >>>hm... i think so

the yellow line doesn't matter, just the combination of pit-timer still running and beeing outside the pitlane is enough to provoke the described behavior from above, also re-entering the pitlane with the timer still running, and the "flooding" stops.