Default Creak/squeak during vibration

Hello everybody, I wrote this also in the official OPO forum, but nobody seems to have my problem. Basically when the phone vibrates (during typing, with notifications or anything else), most of the times I can hear a sort of creak/squeak coming from the phone, probably corresponding to the vibrating mechanism inside the phone. If I try to push through the back cover nothing happens, it's very solid and does not squeak as my old Nexus 5 did. It seems like something coming from the inside. I think it could be related to the vibrating mechanism touching somewhere on the motherboard or any other piece of hardware inside the phone.

Anyone else has the same problem? That's quite disappointing