My guess someone messed up SmartHmi.User.config. Could be willingly or unwillingly. Get a KRCDiag and look into the SmartHmi.User.config. Should be an ASCII file. In the past I had similar issues after people opened files with an (shitty) editor and then accidentally saved the file with a wrong encoding. So the first characters of some lines contained strange characters and Smart-HMI-Config parsers where no longer able to read the files.
If thats the case just restore the SmartHmi-User.Config from their latest hopefully quite new backup. Reinstalling KSS and then restoring latest archive should also work.