If one channel playing up it may be just need a retune to bring it inline with the correct transmitter that should in theory be the same signal level as all the other channels. In some cases it can be related to a faulty cable, failing amplifier and also antenna alignment.
Each group of channels comes via a different frequency and each may be attenuated slightly more or less at various stages. If other channels are fine then it is likely your half way there and a minor increase in signal will equalize the levels.
This same problem did exist back in the old analog days where one channel was a bit “fuzzy” at times or one channel was always “not right” compared to the others. The difference was noticeable more if the wrong type of antenna was used resulting in more signal gain at the wrong frequency. All the other factors still come into play much the same only the results are drop-outs and not “fuzz” as the digital signal is prepacked and not dot by dot.
Different channels different frequency and each needs to have an adequate level to work reliably.
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