Hi @Prew0
There are 3 ways in which your minimum stay may be overridden (assuming you're only using Airbnb's calendar and not managing your calendar through third-party software).
One way is if you have professional tools turned on, and you have created a rule set with a one-night minimum stay that is applied only to certain nights.
The second possibility is that you could have set certain nights of the week to attract different minimum stays. Go to calendar, availability, click minimum nights. You will see the "customise by check-in day" option. Check that one or more days of the week aren't perhaps set to accept 1-night stays.
The third possibility is that you could have created a "custom trip length" for some dates, and that it was set to a 1-night minimum. Custom trip lengths are shown just below maximum nights on the calendar.