I have been using the 740 for years plugged into the cigarette lighter socket with no power issues. After a panel upgrade I hard wired the right angle power plug that came with the unit. Now I have issues with movement of the unit causing it to go blank with no option for backup battery use. It seems that the plug on the new cord is sensitive to movement yet I don't have problems with either the 120v wall wart or the 12V cigarette lighter plug. I checked it with an ohm meter and it doesn't seem to be the plug and wire. Anybody else have any power issues with different plugs? Maybe internal contacts? Maybe bad plug?