Wio Teminal's 5 way switch degradation

I have a problem with my WIO Terminal. My 5 way switch is degrading.
When I bought the device, the only issue with it was I could not click bottom right. After 2 weeks, the OK button stopped clicking, and the switch became little more wobbly. Then, yesterday, the right button stopped clicking, and I had to press it harder to register a click.
2 hours ago, the UP button got the same, but even worse. I disassembled the WIO and I saw that the 5 way switch was slightly rusted for no reason. Also, the plastic covering the switch is slightly lighter in the center and the arrows are a bit blurry.
Why is it? How can I fix it? If I cannot, where can I buy a replacement, and how do I solder it?