Recently I noticed the following lines in the output log window of the UE4.12 editor:
LogText:Warning: Failed to parse argument "GameModeName" as a number (using "0" as a fallback). Please check your format string for errors: "GameMode: Edit {GameModeName}".
LogText:Warning: Failed to parse argument "RootClass" as a number (using "0" as a fallback). Please check your format string for errors: "Select {RootClass} Class".
LogText:Warning: Failed to parse argument "GameStateName" as a number (using "0" as a fallback). Please check your format string for errors: "GameState: {GameStateName}".
...
Any ideas what these warnings could mean?