Part Number: EVM430-FR6043

During commissioning in a ductless, zero-flow condition, an unusual phenomenon has emerged: the two sensors only receive signals when placed directly against each other. If separated by just 2-3 centimeters, signal reception ceases. Could this be due to the sensors not reaching their resonance point? However, even after sweeping the frequency from the lowest to the highest setting on the host computer, the issue persists. What could be causing this?