The settings for generating GUIDs are reset when device returns from hibernation.
After setting up my default for generating GUIDs (uppercase & hyphens) and checking "Don't ask again (use config file)", I used the functionality a couple of times with success and afterwards did not close Notepad++ before putting my laptop in hibernation.
When my device returned from hibernation and I wanted to generate a GUID it did not use my settings, it generated lowercase GUIDs. Opening the config file did show the correct settings but they were NOT being used.