I bought the same camera that you got from Ebay.
I tested it and it looks ok. Although I'm a little concerned about the water proof aspect of it.
The place where the wire comes out, there is no seal at all!
Seems like water can easily enter the camera through there.
Also, the thread sleeve can actually be unscrewed from the body. It would seem that water can enter the camera through the thread.
Have you done anything to water proof any of these areas?
I hope to keep my Impreza for more than 10 years, I would hope that this camera would last just as long...though this camera being $20, I'm feeling less confident that it's going to last.