Ah, thanks for the heads up. I haven't explicitly used lambdas to my knowledge (though I'll check this weekend), but method references instead. I'm guessing those also cause this behavior.
Oops, it seems that roborumble client cannot download your bot, from all over the world. Maybe dropbox set the restriction, or there may be some bug in any of the ends.
And after downloading your bot manually, roborumble client throws exception and exits completely.
Btw, can you try running your bot with robocode 1.9.2.5? And can you try running roborumble to see whether it can download your bot automatically or not?