Grant said:In my case it mainly pissed out of the breather tube, but it could be that the over pressure could push oil out of the gear lever shaft too.
Line of least resistance.
Easy to check oil level though. If level is ok then forget this suggestion.
It's a very plausible argument, and maybe it was over but by the time I'd done 500km it has pissed out the excess and weakened the seal in the process.