Bdogoner

Hi Guys, E70 2011 X5 owner here... My car has the N57 engine and seems it has developed a timing chain noise when cold, not really prevalent when not reving but once give revs sounds like the chains passing over guides in waves. A notable bmw mechanic specialist said in the past they have only done the top chain, and they haven't had anyone come back as in most cases what the problem is - They noted they don't do the lower chains as they have to pull the engine out. Its the difference of paying $1500 AUD or $6,000 AUD and having the engine pulled out. Now the chains were done back in 2021, somewhat 58,000kms ago which i am confused about as to why it would be doing timing chain issue again so soon. Just here to get peoples opinions on what it has been in the past on the N57 taking into consideration the chains were done 58k ago. Also, can you diagnose if the chain problem is the top chain by pulling the timing cover off? Thanks in advance!