[Mike R]

I would be surprised if it was the synchro, as I would imagine it would be a far more regular occurrence (as surely once this was worn, it would do it all the time?). It only does it when hot, so I can only surmise it could be to do with the fluid getting hot and losing pressure and not quite having enough energy to engage the gear (which will eventually end up damaging the synchro as a by-product of the mis-shift?).