Most autokick games have this problem and it’s directly related to how long your computer “hangs” while loading the map. BF2 had this problem so bad that most admin plugins default to a 1-2 minute grace period. The problem is that slower computers can’t maintain their connection to server and load the map at the same time, thus the less intensive is dropped for the more intensive.
The reason you don’t get kicked on your 2nd attempt to join is because your computer already has most of the map files in memory and it takes less work to get it reloaded.