The credit card terminals have recently developed a problem where sometimes overnight they go mad and apparently the solution is to go into Setup on both machines, change one of the settings to the wrong thing, save that, and then set it back to the right thing and save again. I'm not going to say I don't understand how that could happen because I've introduced suspiciously similar bugs in my own code over the years, but it would be nice if someone would take a look at that and fix it.