Being a bit paranoid about the many, many bugs and misbehaviors within AirBnB, I always check several things every single day -- the rates in my calendar, my settings for base rates (weekday and weekend), my base minimum stay, my weekly/monthly discounts, my settings for Instant Book (always, always OFF) and the so-called "Smart Pricing" (also always OFF), plus any custom minimums I might've set for specific dates. And, for the first time ever, I just found that ALL of my custom minimum stays also had a "must start on Sunday" requirement, which I had NEVER set. All of them, even including date ranges that actually started on Saturdays. Clearly, another example of AirBnB's truly horrible coding and/or near-useless quality control. Seriously, AirBnB, you can afford better coding and better QA, so why not give that a try?
If you'd like some help with this fairly easy to solve problem, give me a ring. I've been in the software biz for 30+ years, and it's not all that hard to get it right.