I have a 2017 2552 with the new slide-out.
No issues when stationery but it leaks like a sieve when driving at speed in the rain. After extensive testing with a hose (hard to test when driving at 50mph), I believe the issue is a combination of the rubber gasket on the top seam AND the drip spout at the leading edge. It seems to require both a slight gap in the top seam gasket AND the drip spout forcing water back along the seam. The top gasket alone will not generally leak, but at high rates of speed the drip spout acts like a funnel and shoots water right at the top seam, if there is a gap in the gasket it will then leak.
I fixed (I hope) the issue by filling the rear of the drip spout with silicone to prevent water from flowing backward through it. I also caulked the top seam with silicone as far as I could reach. Once I figure out how to detach the slide topper I am going to caulk the remainder of that seam.
I just received an email from Kermit stating that they were now filling the back of the drip spout and caulking the top seam with silicone, so it seems the factory diagnosed the issue the same as I did.
I have no issues with the Lippert-Schwintek mechanism itself, it seems to work just fine. So as long as the additional caulking fixes the leak I would have no problem ordering it again. I'm calling this a 'teething pain' for a new part and install. And again without that drip spout, I do not think there would be a problem anyway. Just a freak combination of factors.