This is a known bug with some Ubiquiti devices. But it should be fixed now in 23.05.3. You will need to install via TFTP (i.e. factory installation method), but once that's done, you should be able to save settings.
From the 23.05.3 release notes:
ath79: Nanostation Loco M5 XW: Fix read only jffs2 partition