Hi there,
So I haven’t received this one yet to test with but I would offer this. The millimeter wave radars are a new area in IOT you can check everywhere it’s a dark ART to get it perfect and the environment has to be pretty close too. SO that being said.
If the mount it is connected to is moving vertically ? even a millimeter and if the sensitivity is set very high it will trigger makes sense right?
I have a demo on here of the discrete board connected to a xiao directly and the accuracy was very high albeit the environmental requirement were specific to get repeatability. YMMV
You may need to add some kind of dampening material under it or move it closed to the adjacent wall. I had a similar situation with testing and required a mini Gantry (see pic)
HTH
GL 
PJ 