We just bought this from eBay as a ‘new condition’ item, but had damage to the packaging only.. set it up to find everything worked apart from the distance, speed and timer. It weighs a lot, and I didn’t particularly want to return it.. but it turns out it isn’t hard to fix.
There is no way this ever worked.. the sensor wasn’t over the top of the magnet, and was glued into the receptacle. I wedged a screwdriver into it to crack the superglue, and then I could adjust it to position it over the magnet. My fallback if this hadn’t worked was to glue on one of my kids’ more powerful magnets 🙂
Here’s an Amazon link to one really similar to the one we bought; https://amzn.to/2D8Xu4L