Sonoff Motion Sensors - These are Really Bad

I installed 6 Sonoff SN-ZB03 motion sensors this morning, and I'm getting so many false positives that they're essentially useless. I could understand having one that's bad, but 6?

Three of them seem to randomly trigger for no reason at all. One triggers any time the heater comes on, regardless of where I place it. The last two usually work but still give random false positives.

From what I'm reading, there are a lot of complaints about these. I probably should have done some research before I bought them. I can't shake the feeling that I'm doing something wrong. Is ITEAD really selling a motion sensor that just doesn't work properly?

I don't see any commands listed under "Manage Zigbee Device" that allow for a sensitivity change, and I can't find a datasheet or a manual for these other than the basic "quick start" guide. As far as I can tell, there's no firmware update available, either.

Am I stuck replacing all of these? If so, any suggestions on better ones? I've read good reviews of the Hue motion sensors, but they're not cheap.

EDIT: I've had some time to experiment with these a bit more. They can be made to work, but only in very specific circumstances. The ones I had outside would trigger constantly, as would the one I had in a room with a heater. They also seem to interfere with each other if they're too close to each other. I placed one in an attic area, and one in the stairs leading up; these are working flawlessly. So if you need a motion sensor for an indoor area that isn't climate controlled, doesn't have another sensor nearby, and doesn't have frequent lighting changes, these might work. Maybe for a closet? I won't be throwing these away, but there won't be a lot of cases where I use them.