I'm sorry to hear you are going through this hassle. I think it might be related to the external connections you might have set up. Like you mentioned PriceLabs. From my experience, I used to have Lodgify to manage my listings cross platforms and availability was managed through Lodgify. It doesn't sound like your case, but there still might be some connection behind the scenes that restricts your availability. I learnt that these type of connections are not very straight forward and there's some complexity when setting up or disabling them, so you might want to ask PriceLabs again or check whatever info they have in their documentation. One more thing to check - sync calendars. If you have your airbnb calendar synced with any other calendar (e.g. another hosting platform) you might have restricted dates coming from there.
Finally, just occurred to me! You said you turned smart pricing off. In that case you are supposed to enter the prices manually. However you said prices are managed by PriceLabs, so if they for whatever reason did not provision prices for those far future dates, then your calendar will not be bookable. Try testing it and manually setting price for some far future date, then see if it is bookable. I am really thinking the limitation is coming from PriceLabs. Also can you think of what is the date 19th of September 2025 about? Maybe it's your PriceLabs contract renewal date? Or maybe they only commit to predict prices ahead of fixed amount of days and it falls on that date from today. They might not even know that airbnb blocks those future dates, but if they confirm that they do not feed the prices into your airbnb calendar beyond specific date, then you know your far future dates will not be bookable as they are missing prices.
Hope that helped. Sorry for long message. I hope you can find the root cause and would be nice if you could share it here 😉
Good luck!
Cheers,
Liza