I go into more detail on why this happens in this post:
Long story short, these fluctuations are expected, and the distance estimates is something you need to take with a grain of salt—the average error is, as I mentioned before, about ± 20%.
If you only want to know what pallets are within 4 meters, you can tune the broadcasting power of the beacons down to -20 dBm. The average range of a beacon with this setting is about 3–5 meters, so you won’t even need the distance estimates—instead, you’ll be able to rely solely on the fact whether a beacon is or isn’t in range.