If Suneido crashes (or the process is killed), then the next time you run it, it will require a rebuild.
I am not sure why the code page would make it crash. It might cause something to fail e.g. in Init or somewhere else in the GUI, but that should not cause a crash.
The database itself doesn’t care about character sets or code pages. It just stores 8 bit chars. Changing the character set or code page will not make the database invalid or cause a rebuild. If different clients interpret the data in different ways then that could cause problems.
To compare client to server, you can use ServerEval to run code on the server e.g to get the language setup.