Mark wrote:
"It is very unusual for the RF path loss to be non-reciprocal".

Yes. I believe the radios and antennas were exchanged with the same
results. So, even if separate frequencies are used in opposite
directions, the impaired direction, which was reported as unchanged,
indicates something wrong with transmission not reception at the fixed
building location. Any street location seems deaf. Perhaps there is
interference up and down the street.

Best regards, Richard Harrison, KB5WZI