McCafé B5G1 scan not working

The McCafé Buy 5 Get 1 Free doesnt show up every time when we buy & scan. Two out of three times it didnt register our purchases. :( Needs to be fixed, or go back to the sticker method where we collected 5 stickers on a card and turned it in for a freebie. Thanks!

Dozermom about McDonald's, v5.4.1