The password cannot change itself, but it is possible for a third-party (be it a person or an installed application) to change it. Unfortunately, the only two ways to hard-reset the device are using the hardware keys (nonfunctional) and software switch (inaccessible without login). Thus, unless you have a third-party application installed that enables you to hard-reset remotely, you'd have to ship it in for service, which I'd recommend anyway since the hardware keys are not functioning.