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Hmm, I know I've seen those kinds of errors before, but beyond clearing robots/.data and robots/robot.database and rebuilding, I'm not sure what to try. Can you actually run (eg) XanderCat 12.0.1 or is the bot itself broken too?

Certainly no harm in trying a fresh Robocode install. I've probably got like a dozen. :-)

The bots run fine when Robocode successfully starts-up.

I don't think the errors are causing the problem, but they might be symptoms of a larger issue.