Probably χωλόν is right, but it beats me what the Tarentines were up to. I suppose it's possible that their "game" was actually a poetic contest, that the adjective τραγίσκιος designates a genre (like βουκολικός), and that the "limp" had to do with the meter of the song/poem (cf. choliambic). In other words, ἐξάγω χωλὸν τραγίσκιον could be, like Aristotle's οἱ ἐξάρχοντες τὸν διθύραμβον (Poetics 1449a), "begin the limping goat-song." But that's all pure speculation.