I have 6 Bravia TVs connected to a central media hub with both coax aerial cable and HDMI cables. Some of the TVs have poor or no digital signal on many of their channels. This problem can be solved by simply unplugging the HDMI cables. I have tried switching coax and HDMI cables without solving the problem. Various internet forums suggest this a widespread problem and is particularly bad with Sony TVs. Is there a recognised solution to this problem?