People must realize that when any of the newer directional antenna systems are used, your disappointment may actually be caused by poor coaxial cable connections. This means starting at the connection first at the antenna on the roof and following all connections to the antenna power plate in the wall, connections from there to the "BOMB" (switch-box) routing all TV's, cable, OTA, and dish).
Any loose connection can cause loss of channels. Coaxial cable connections can easily be loosened by vibrations while traveling down the road.
Many Class A motor-home builders make it very hard to get at the back of the "BOMB" or TV to check for a loose connection. That is the reason why I kept my Class C were the "BOMB" and cables are all in easy reach just sitting on the shelf in the overhead cabinet.
The antenna itself may not be the problem, if no one did there job in checking all connections at installation time.