Lost Signals

Since I have installed my mini b boxes I am getting intermittent lost of signal on a consistent bases. I have four mini boxes and two regular boxes. The lost signals occur on all of the sets that are connected to mini boxes. The problem does not occur every day just a couple times a week. I have checked all of the connections on all of the boxes and since this does not happen every day I have to assume that the connections are good.  Does anyone else have this problem?