After receiving my RetroFlag GPIcase and install the Retropie image if found an issue with the slpash screen intro.
The intro will start, but everything is in slow motion. Also the music is lagging.
Very long time on google to search for a solution. Nothing.
Then i found one site where the error was descibed. And here finally the solution.
You have to change the boot.txt file. For me it was not possible over Putty / FTP.
Because the file was locked.
So remove the SD card, put it in your PC or Mac and edit.
Then go to the end of the file and add following:
This should solve then your problem. 🙂