When there is terrain obstructing the path between the transmitter and your location, your TV Fool report will indicate one of three possible degrees of severity: 1Edge, 2Edge or Tropo.
The
TV Fool report posted in
your previous thread, indicated that the WJZY signal was '1Edge', meaning that you have some terrain blockage. This can result in the signal being more variable in strength and quality. Even though another station may broadcast from the same tower, the difference in transmitter frequency, antenna height and antenna properties can result in the signals being affected much differently during the trip to your receiving antenna.
Have you tried moving your antenna up, down and laterally? Sometimes, a move of just a few inches will put an antenna into a significantly better or worse area of reception for a given signal.