My one-way on RDX started to free spin. Just on left hand side (3 wheel drive)
Iíve tried flush out one-way bearing with motor cleaner then used one drop of bearing oil. It came back good for about 1 lap then lost drive again.
Is there any way to fix this or do I have to buy new one-way?
You may need to get a new one way, as the bearing seems to be worn. It's unlikely but it could be the outdrive itself, try switching around the front outdrives and see if it's still slipping on the same side.
Oneway bearing needs plenty of oil, a dry oneway bearing will die in no time. Even a new oneway bearing will slip if there is no oil. Try some oneway oil from x-ray or serpent, add 4-5 drops per bearing.