So, while updating to 184.108.40.206 fixed a badly broken TeamBot situation, it introduced a new problem that I first noticed with Tron. The precise cause is unclear to me at present and can't debug into a closed bot that isn't giving a stack trace, but some change between Robocode 220.127.116.11 and Robocode 18.104.22.168 appears to have broken bots that load data files that come preloaded in their JAR files. In the case of Tron this is used for a configuration properties file, and being unable to load this is causing Tron to start in challenge/reference mode instead of normal mode.
I'm doubtful this bug only affects Tron, and removing tainted data from the rumble could be troublesome.
Bug report: here