Restoring Larch wood cladding

[T5GRF]

Our garden room is 3 years old and despite two coats of OSMO when new the Siberian larch cladding is starting to go grey/black in places as the OSMO has failed.
Is it simply a case of sanding back the areas and reapplying a coating to protect? This would take some time to do as the building is 12 meters long. I was wondering if the areas could be cleaned up with sand or dry ice blasting to make the job easier?
I know there are wood reviver products but the building is surrounded by composite decking and has aluminium windows both of which could potentially be damaged by the acid used in these products.
Any other advice welcome.

[T5GRF]

We like the colour and appearance of the wood cladding when not ‘weathered’ I’m quite happy to look after it hence coating it with OSMO when new, I just don’t fancy spending days sanding back the weathered areas if there’s an easier way such as ice or sand blasting.