fix step-down detection

ttrs.py

@@ -266,8 +266,6 @@ class BalanceTtrsPlayer(TtrsPlayer, threading.Thread):
             print('player_id=%d xbal=%d ybal=%d' % (self.player_id, xbal, ybal))
             if xbal == -128 or ybal == -128:
                 self.evt = PlayerEvent.QUIT
-                self.running = False
-                break
 
             THRESHOLD = 40
             if abs(xbal) < THRESHOLD and abs(ybal) < THRESHOLD: