Mate I have almost the exact same problem! Woke up one morning to find the volume button on my nexus 6p bent inwards near the top! never dropped it or anything but I think even light pressure on it from an awkward angle can cause this - even if it leans against something exactly there with a little pressure can cause it to bend inwards. I've contact Huawei and apparently im getting a jiffy bag to send it to them in. I just wish I could have got it directly from google as they are more understanding from what im reading and the last thing I want is issues with Huawei issuing an RMA on a device that seems quite clearly vulnerable at a crucial component! Theres many other people with the exact same issue unfortunately.