Can't add more flights on my largest airline

I run what is currently the #4 airline on R3. Starting last night after I bought and leased a MASSIVE amount of planes from the 4th biggest airline which got deleted, I noticed I started having an issue where I couldn't add more frequencies to flights. This wasn't much of a problem at first but now I can't do it at all. For example CDG-WAW, I go to the add flights menu, put in the amount I wanna add, and when I hit add flights, nothing happens. I also can't lease more gates for warsaw or any other airport I try to add flights to. I've tried multiple different browsers as well as restarting my computer and trying the mobile client, same issue through and through. I tried another airline of mine that's based in Poland, and it seems to work fine, so the issue seems isolated to my largest airline for some reason.

If you have more than 1000 airplanes on the add more flights page it will not let you do anything.  Filter by type to reduce the number and try it again.