I've run into the exact issue even when the problem transmitter is on the same tower and even when it emanates from the same antenna as a station that is not having problems. Every frequency is affected differently ever-so-slightly by impairments in a given path.
The final few hundred (or dozen) feet can make or break reception. It's usually a mistake to assume that ALL of the incoming signals will arrive perfectly in the particular spot that looked convenient for the placement of a receiving antenna.
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