I am having a( Free play) save setting issue on two Stern machines , FG and SM. When going into the settings and setting each machine to free play it reads (Installed) just as they should. But then when I exit out the setting reverts back to being not installed. I have double checked both coin cell batteries and they both read 3 volts ,as they should. I am at a loss here and am growing tired of opening the doors constantly to add credits.