Has it recently had a service done?
Are there any new "odd" noises from that area?
Is it easier to stir the box, if the engine is not running? If so, the clutch may be dragging. Check the cluth master cylinder fluid level, and pedal adjustment, also if the push rod in the clutch housing has worn down to much, as some do. (A messy job sadly...)
(I'm assuming the 2010 Defenders still have a hydraulicly operated clutch, if it's cable by now, check/adjust that as needed. Cables can stretch.)
If it's still dificult with no engine running, try checking/changing the gear oil. It probably should not have EP90 in the modern boxes, I think you usually use ATF/AQF, or even engine oil if that is not available. Consult the manual to find out what should be in there.
Regards.
Dave B.
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