Thats weird. I've had a lot of my grills outside with no cover for 3-5+ years and never had an issue like that. The MAK had an issue where the screen got fried by the sunlight. Apparently, they fixed that with a newer model controller which I have installed and have not had an issue so far (2-3 years).
What's interesting is I had another "stainless" grill that started having "rust" issues a few years back. I always had that grilled covered.
Got a replacement and quit covering it and the issue never happened.
I have a cover for my Q450 and have barely used it. Grill in rain, snow. It's been covered in ice, snow, rain. I'm curious how long the controller will last, but part of me thinks not having it covered is better so it breathes freely rather than trapping moisture inside.