Volumne up button permanently on

If it's acting like it's always pressed, that could mean a few things. The button might seem like it's prettying externally, but there could be some dirt, or the alignment of the button might be just off. If it was every dropped, there could be some damage there causing the button to always read as depressed.

Your best bet is to open it up and have a look at the audio board, where those buttons are mounted. See if you notice any damage. Try pressing the button directly on the board if you can to make sure the actual button is working, you should be able to see exactly what's happening if you look closely with the back panel off. Most of the external parts of the button are just flexible membranes so it might feel like its clicking even if it's not. You can use a spudger, or some other tool to try to engage the button since I usually recommend against trying to poke circuit boards if the device is powered on. It's possible it's only a little stuck.

If that doesn't help, take the board out and clean around the button with some isopropyl alcohol and a cotton swab. Otherwise replacing your Audio board should do the trick.