Power button not working

Device situation:

• The phone has a thin rubber case.
• It has had a few falls at around or less than 1m (3ft).
• The screen and rest of the phone are fine, no cracks, very few dents
• It went for a 3 second swim in the toilet (luckily just after cleaning and before using), I turned it off and placed it for 2 days in a bag of rice, which seems to have fixed it.

The problems:

The phone has 3 major issues, the power button being the focus in this post, however to be thorough I want to mention all here:

• camera partially blurry
• power button not working
• very poor connectivity on wifi (have to constantly put plane mode on/off to get internet back)

Further description:

I have not noticed a direct relation of a fall/swim to the power button issue.

I was able to get the button working again once after a complete reset of the phone, but i think this might have been complete fluke as the same day it stopped working again.

So of course my temporary fix is to use the software button.

All other buttons are fine (they work), however the audio toggle is very stiff, which leads me to think my phone has collected quite a bit of dust in the past 3 years.

Questions:

Is it possible that the buttons contacts are full of dust, therefore it cannot function?

Or maybe the water from the swim did some damage and it needs replacing?

Do you think (like I do) that my phone needs a good dusting/cleaning inside?

I'm asking before opening because I have damaged an iPhone before, and only want to open if absolutely necessary

Thanks

Questions regarding the other issues mentioned here:

• Rear camera photos are partially blurry
• Wifi connectivity is inconsistent