Sounds like a knock from cylinder 4, oil analysis clear, good oil pressure, compression ok, runs perfect up to rev limiter other than noise / knock.
Bit of a mystery to be honest
Just stumbled across this thread as I’m looking to rebuild my 4200 engine ( knocking noise at 1500rpm when hot)
Are there any updates? I see by mot history it’s not on the road since 2020
Cheers