HELP! Churning noise from front only when reversing and can smell burning

[b3magic]

Hey!

So last Monday I had this issue after a short commute I reversed onto my drive and heard for the first time:

Churning noise when I press on throttle from front of car seems like under drivers footwell and then instantly I got an oil burning smell and like the exhaust has heated up.

Not happened again until tonight!

Same again, so I went around the block.
When driving away or stationary and I rev the engine there is no noise ONLY in reverse it was still making this churning sound and the smell of burning was getting worse.

No lights or codes on dash!

I have it booked in with dealers but warranty is up soon so I am worried if I get told unable to reproduce the fault.

Any ideas?

Cheers!