Had same problem with my 825i. Dealer said the engine has hydraulic lifter that never needs adjusted.
My issue was that the engine had dirt and sand in the oil. The dealer couldn't explain how it got into there, but basically it was my responsibility to pay for a new motor. Had the same issue again with the new motor.
Hope you get it figured out. Do yourself a favor, keep a log of your issues, when it happened, when you notify the dealer, receipts, etc. I'm currently suing JD over the lemon they gave me...I had to scramble to come up with all the receipts.
it turns out that quite a few of the Gator rsx'swere not broken right at the factory and the cams or developing flat spots they are pulling a cam out of another Gator to put it in mine because they don't have cams in the States they would have to have 1 shipped here from Italy but supposably I should be getting it back on Friday