When I try to boot the game through the Steam play button, I get an error stating that ffxivboot.exe is missing from C:\Program Files\SteamLibrary\steamapps\common\FINAL FANTASY XIV Online\boot

I don't have FF14 installed to my C:\ drive because it's full. I have it installed to another steam directory on a separate SSD.

I've tried reinstalling the game and it works for 2-3 days and then gives me the error again, warranting another reinstall.

This only started after Steam account linking was rolled out and I was forced to start using the new launcher.