Jumping gears

[Snooky]

53 plate 1150gs, jumps out of gear 5th down to 4th or sometimes needs a good kickin to get in to 5th, is it me not used to the gear box or do I have an problem in there, still in warranty.
All other gears are fine and normally happens when givin the thrttle some stick, but has been a pain at normal operation.

 

[littleredrooster]

Check the gear-linkage ball-joints for lubrication, as they can cause this problem, also the shaft where it goes into the gearbox.