It was even worse in my case, as I could not even take normal videos, it would show the same error “HFR is not supported for selected resolution" as if I was trying to get slow-motion.
Fortunately, I found the fix: in the settings (top-left gear), the Video Encoder was no set. If you clicked on the setting, you’ll notice two options with a radio selector, MPEG4 and H264, but none of them was selected. Selecting either will fix the issue for normal videos.
I still cannot take slow-motion videos, but hope this will help people having the issue for normal videos.