I'm definitely not able to reproduce that. It almost sounds like something really bad happened to the configuration files and the changes you are making aren't actually being saved as a result of this. If you want to email all of the .xml files under C:\Users\<your username>\AppData\Local\Packages\41730Zubersoft.MobileSheets_ys1c8ct2g6ypr\LocalState to mike@zubersoft.com, I can take a look at this, but it sounds to me like it may be worth resetting the application settings to the default to have a clean slate. I can also try to fix the configuration files for you and send them back if I'm able to locate the problem. Alternatively, if you have a library backup file, you can restore that and it will replace the settings files.
Mike
Mike