I've had this for awhile now, driving me crazy. It happens with or without someone, my son says it is above his head. I took the tops off and checked the bolts for the rear cargo top even put a piece of tape in between. It stopped for a little while and then started again.
Apparently when I was reading this thread, many had responded and at the time it was not posted... weird, but I found it.
New question is, how long did it take to arrive?
I typically follow your rationale here when I buy, but I got a 2020 Explorer ST with 0% so I pushed it out as far as I could. Just wondered if you would have done it too since we seem to think similar.
I did get a decent rate for my 2022 Wildtrak, but not 0%