|I have the same computer. Alas, I have no such problem. Otherwise this is most likely a very simple problem.|
Your battery is most likley not at fault; the button is the most probable culprit.
Like most tiny push-buttons, as the power button on a laptop is, they wear out over time (think clicked-to-death mouse). This is most likley the case, if you have used the button constantly or put undue pressure on it. At this point i don't know what to tell you, besides bugging some poor tech at a repair shop to replace it.
But it is possibl it is just a piece of garbage wedged underneath the button not allowing it to fully depress. Does the button click or not? Try using a can of comppressed air to clean out underneath the key. You may have to remove the small pop-off panel that covers the area above the keyboard to get underneath the key fully.
Let me know if this helps.
EDIT: Obviously, leaving a system on 24/7 is not good for long-term longevity, depending on when you plan your next upgrade.
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