In case anyone else has had this experience, I have smart pricing, however for certain dates I overwrite that price with a set price - weekends, public holidays, Christmas etc. I just noticed the set price was overwritten by the smart price and someone booked at Christmas at my base minimum. So I had to tell the guest something has gone wrong. I had to call airbnb and report it and ask them to cancel the booking. I noticed this Friday 24th till Sunday 26th. Check your listings everyone! Another airbnb glitch