I found this thread while looking for a replacement robot for a 9300 Polaris unit that died on me. I was debating vs the M400 and the S300. I got the S300 today and used the old Polaris unicover drain cover (UFO) to make a ramp around the drain, same as Sk1dM4rk. My renovated pool came with high WaterWay grill.
The M400 Demo unit I tired has no issues with the drain. Great unit but I found it too heavy for my family to take out from the pool. was getting scratched on ruff texture of the pools concert bull nose finish.
I am very anxious to see if the S300 will get stuck with and without the UFO. Local pool shop sales person was told me received no complains of the S300 getting stuck on covers. Are you robot similar to the S300 ?
Picture of a spare drain grill with the Polaris cover center section craved out with a dremel
Still a bit of a bump with the cover UFO on the grill