The impact of the hammer is at an angle and not perpendicular from the accelerometer face.
The hammer impact is too high axially on the endmill in relation to the accelerometer location
The impact of is not opposite and perpendicular to the accelerometer face.
If the hammer tip is not aligned an overloaded impact may register a false positive response. If the coherence is not considered, then the resulting Dashboard may be inaccurate.
Too much wax on the Accelerometer can absorb some of the force and decrease the coherence. Apply just enough wax to adhere the Accelerometer to the tool.
If the coherence is just below 80%, the first thing you should do is try the tap-test again (“can you repeat what you just said”) by clicking on the re-practice button. Go through the practice taps and then click on the Measure button to take the measurements again. Make sure you are tapping with a solid motion and land solidly on the tool tip directly opposite the accelerometer.