OTA signal loss on one channel only?

My bedroom 612 receiver has lost signal on one of my local OTA channels (CBS). The other local channels come in fine. The strongest signal is about 88 on the bar and is with NBC, with other channels also in the lower 80 range. But CBS (both of their digital and HD channels) show the big yellow pop-up on the screen that "signal has been lost". CBS is in the same antenna direction (to the South of me) as the others. Although I live in the country, I have a big Channel Master high gain antenna atop a 60' tower and I've never had trouble before with my "locals".

My main receiver is a 622 and is located in my den and it picks up the CBS OTA channel with no problem. For some reason, the 622 must have a stronger tuner than the 612 because it shows all my other locals at 100% signal strength although the CBS channels are shown at about 73%, but still come in perfectly on the 622.

Could it be that because the 612 does not show as strong a signal strength as my 622, it simply can't lock in the weaker CBS channels? The problem has only started in the last week or so. Any suggestions on what to try?

No, I have not tried a rescan but I will. The run to the 612 is about 50' longer than the 622. So, yes, that could be a problem but it is one I never had before. Another thing I will have to try is moving the rotor slightly. My antenna is on a 60' tower and may have gotten knocked out of my original setting by the wind just enough to not see that channel. My other channels are all good and CBS tower is in the same direction but that is something else I can play with and eliminate as the cause.