I also have a 2018 Chateau, and I've had lots of problems with the blinds. The most common problem is that they won't stay closed. I've had this happen to nearly every blind in the coach, and twice on a couple of them. When it was under warranty I got replacements from Thor or via a service center.
I'm not positive who the manufacturer is, but I think it is MCD Innovations. Regardless, they make similar roller shades and you can get replacements from them. RecPro is another potential source for RV roller shades.
I have taken these shades apart to try to fix the mechanism, but didn't have any success.
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