Middle Mouse Button Measurements in 'Front' mode measuring based on Y location

When using UE4 in Front mode, using my middle mouse button to measure distances, I am receiving some strange results.
The measurement will add the value of the Y location to the measurement, giving an inaccurate location.

This is obviously a feature, but it is really messing me up. How do you disable this feature?

The solution is likely very obvious, but it escapes me, and is still hindering my progress. I’d appreciate some advice.

Anyone have any knowledge that they can share with me?