Assuming you are correct that there is free space available, there are a lot of weird bugs with NTFS under Linux so this is probably one of them.
I assume the NTFS drive was connected to Windows at some point. Windows can sometimes leave the drive in a dirty state which can cause odd behaviour. Windows fast startup feature is enabled by default and what it does is prevent the system truely shutting down when you click shutdown in order for the next boot to be faster.
Windows fast startup causes some people who multiboot to have issues with wifi/bluetooth not working in Linux without forcing a hard power off or booting into Windows first then rebooting into Linux. So it is recommended to disable Windows fast boot when multibooting. https://wireless.docs.kernel.org/en/latest/en/users/drivers/iwlwifi.html#about-dual-boot-with-windows-and-fast-boot-enabled
My advice is to avoid using NTFS as much as possible in Linux. Many people try share a NTFS drive for their games between Windows and Linux and have nothing but issues which magically go away when they just use a Linux file system for their games when in Linux.