If you search the forum for WH57 accuracy, issues, etc..
You will find a ton of posts on the unit. In my experience with the one I have, it works, it detects, that is about all I can say.
I would not consider this a precision sensor, and personal experiences vary wildly from false strikes to not registering strikes if you search as mentioned above, I may be lucky , not only with the unit , but maybe my geographic location lends itself better for the sensor.
Interesting that you are considering buying a 2nd one