Not sure if this is already in the database, but changing the guild name in the guild books from capital letters to lower case letters brings up an error.
Changing the name PHOENIX RISING to Phoenix Rising brings up an error and name cannot be changed.
I should add that after I received this error originally, I tried changing it on the books from the old guild, whose name was all lowercase letters, up to all upper case and that worked out perfectly. Couldn’t change it back to lower case either. Now, that old guild name is stuck in all upper case letters too.
Yes, there’s definitely something odd going on with capital letters since I was able to reproduce a similar situation, so thanks for the report and screenshot. I’ve added this to the bug database.