It seems like whenever your scheduled a shift that extends from one week to the next i.e. Saturday night into Sunday morning it glitches and causes errors in the next weeks schedule. When full week view is selected the errors go away for me.
At the electronics registers we get prompted for service plan eligible items then we press k1 to add the plan. I'm not sure exactly how this works at the front lanes since they usually don't prompt for them. I will find out the exact answer tonight.