It is not a bug..
The kick for 'unstable connection' is NOT based on high ping. It's based on how stable is your ping to the server. Even though your ping is very low, but if it keep spiking (meaning it is not stable, e.g. ping of 30, 20, 800, 80, 50, 1000) then you will get kicked. Based on log, most kick were because of ping that suddenly incease to +900. You might not notice your ping had spiked but the server does not stop recording your ping while you play..
Anyway, the server only kick players that are spawned and not 'away', so make sure to pause download and turn off background processes that heavily use your internet before you spawn/play.