You have a warranty, use it.
IMO, giving you suggestions on what it could be only creates more headache for the service manager ... you thinking you know where they should look, the internet told me, etc. Also, if you tell them what you think it might be they may verywell overlook other things missing something.
So I offer no advice. Let the paid pro's deal with it.
Don't "think outside the box".
There is no box.
Do it correct, or do it twice.