Okay, for some reason, the screen command needs an sh after the -L on a Raspbian-based Retropie. sh starts a new shell with the script in it. On my Desktop PC running Kubuntu Linux 18.04, the command works without the sh, but on my Raspberry Pi running Retropie, it needs the sh to work as intended.
Whatever, please try this with an sh behind -L:
screen -S bezelproject -L sh /home/pi/RetroPie/retropiemenu/bezelproject.sh