I have a 2015 Ultra Limited Low. My problem is that it squeaks extremely loud anytime you go over the smallest of bumps. I have had it in 4 times to the dealer for them to stop these squeaks but they cannot find it. It is sill under warranty and this began immediate after I purchased it. Any ideas what could be causing this. The last mechanic told me they have checked every bolt and connection and can't find the cause.