The only time it would act up is when there was hold announcement. For example, shitty music would be playing then " you know you can save time by doing this online" would trip it up but it got way better after a couple months.
My zapper is still acting up. I can only do about one zap a day and it's random when it wants to go through. I think I figured out the issue but just need to find a little time to mess with it.