The tuners in different devices will always have some variations in how well they receive different channels, based on the strength of the signal from those channels. The strength of the signal from TV stations can vary at different times of the day, and there are also seasonal variations that can occur. This means that a TV station may appear to have good signal in the early morning, but drops off completely later in the day. These types of signal strength variations are normal for over-the-air TV and radio signals. The tuners in set top boxes and in TV sets also have variations in performance due to the tolerance of the components used in those tuners. Although the variations are frequently minor, when trying to view weaker channels, it is possible for one tuner to be able to pick up the channel while a second tuner, even from the same manufacturer, may not be able to receive the same channel.
One possible solution for this is to add a preamplifier at the antenna, or, in multiple TV set homes with several TVs connected to the same antenna through splitters, the use of a distribution amplifier may help. In both cases, the amplifier will provide a stronger signal to the TV or set top box tuner, which may help it to receive the channel.