Hi the same happened to me, I contacted AIRBNB and they told me that it was because of the currency change. I was supposed to get 159euro per night and instead got 148 euro per night. They told me that the guest had paid 170 dll, but that does not equal 159 euro so my min price was not respected. Also I had people from the USA before and this had not happened. I told AIRBnb that and they continued repeating that all was correct. If it says min price it should never be under the min.
Anyway no answer and was hoping for somenone to explain more about this. Hope someone answers you Ronnie to clear things up.