The most common cause of failure of these two switches is drop damage. If the aluminum casing is impeding the buttons, you might be able to pry it away from them. If this doesn't resolve the issue, then the switches may have been damaged internally- they are mounted to the rear panel, as shown here:
I would NOT spray any liquid into the iPhone! It is always energized, so you will likely short out the device.
It might be worth the effort to remove the rear panel and attempt to work the aluminum and switches back to their proper shape, and if this does not resolve the issue, the replacement part sold here on iFixit appears to contain new switches:
[produit lié absent ou désactivé : IF105-000-1]
Check with sales support before ordering to confirm this...
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