I have a first gen Magnus being controlled via Giga-Blue on a PC with Rouvy. It is in a room converted to a training room with a gym floor, fans, etc. I have the room isolated from the heating system so I can control the temperature at 65 degrees, so its not an 80 degree sauna sufferfest.
I was doing a virtual ride in Rouvy that ride goes up 2990 feet in the first 6 miles, then goes down for the next 12 miles. That puts it at somewhere between 8 and 12% grade for a 6 mile climb. With my weight and FTP that meant that I could only hold about 280 watts for the climb, my cadence was around 60 rpm, and I was moving at a virtual 6 mph. About 25 minutes into the climb the trainer reduced its resistance. My power dropped to about 190 watts and my speed dropped to 4 mph. I shifted to correct and the power would not go up. The more I shifted the faster I pedaled, the faster the back wheel spun, but the power and speed would not change. At the top I would normally shift up to fly down the hill but I didn't have to. The power dropped but the virtual speed jumped to over 30 mph, and I was still spinning a 39/17. Obviously not possible in the real world.
Saris told me that the Magnus was never intended to grind away at low RPM and high power (I guess 280 watts is considered high power) and the trainer will drop the resistance to protect itself. He said that the software makers are trying to "one up each other" in this area and its causing problems for the hardware makers. Peter said that all smart trainers have that problem in one way or another. There is no warning or indication that the Magnus is going into protection mode. He said there is a firm wear update coming soon to make the problem better, but what I should do is install a fan to blow directly on the resistance unit.
I don't know if putting your trainer into thermal protection mode once a week will shorten its life, but it can't be good for it. I now have a little fan on the floor dedicated to keeping that unit cool(er). I haven't put the fan solution to the test yet, but hopefully it will at least mitigate the problem.
"...the street finds its own uses for things"