It's disheartening to hear about these leaking problems. This is only my third year using Earthboxes, but I had heard they last 20 years or more. I hope you folks with leaks find a way to remedy the situation.
The wheels are of no use to me, as mine are in the back yard and not on a solid surface, just weed barrier on the ground. I'm not sure I would even know if any of mine had a slow leak. They are all adobe colored, so I hope that doesn't have anything to do with it.
I own nine of them, but I have since learned how to make sub-irrigated containers using 5 gallon buckets. I have four in service this year. They do get brittle in the sunlight over a few years' time, but they're cheap to make and easier to move. The two jalapenos and two bell peppers are doing great in them. Buckets have their place, however Earthboxes hold more soil, better accommodating larger plants such as heirloom tomatoes, which have massive root systems.
I have been recommending Earthboxes to everyone I know, so I really do hope their quality is the same as it was long ago. It's a great system, and it would be a shame to be undependable after so many years of success.