My ACW4 keeps going out of service and says $1 input stuck and there is usually one bill on top that didn't go into the stacker? All I have to do is press the bottom button and it says error acknowledged and resets it, but it's just a matter of time and it will do it again. It's been happening now for the last week or so and it's done it before in the past. Mysteriously it will not do it for months and then when it does start to do it, it's pretty frequent. Anybody else have this problem? What did you find the problem to be?