Hi, first time around here

. I verified this thread for an issue similar to mine, without success. I got my Nexus 9 from Google Play a week ago. It is the white 32GB wifi model. I found another issue similar to one described around here about auto dimmer not working properly, which I "resolved" for the time being by turning it off. The other one is more serious, and it refers to the "Home", "Back" and "Multitask" buttons becoming unresponsive. I have not being able to pinpoint a specific app or action starting this behavior, expect perhaps for moving from one open app to another very quick. If I wait for around a minute (more or less) without touching one of these buttons, they start responding again. I get the same result (recovering the buttons' functions) if I briefly press the power button to lock the screen and then unlock it. It does not seem to be a general freeze, since I am able to keep using the app I have being using when the buttons become unresponsive.
My main concern is whether this would be a software or hardware-related issue. So any hint will be very much appreciated. Thanks in advance and just let me know if further info is needed.