Digital tuners can develop - Digital Glitches - that are not cleared out with simple channel scans.
Do Double Rescan.
Disconnect coax from Tv.
Scan for channels.
Disconnect Tv from power.
Wait a minute or so.
Reconnect Tv to power.
Reconnect coax to Tv.
Scan for channels.
http://www.wchstv.com/DoubleReScanAlert.pdf.
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http://en.wikipedia.org/wiki/KUPX-TV.
Call the Tv station , information from the engineering department.