There are several things that can cause a light reflection to appear on your photos.
1. Make sure that the roadcase door is completely closed, in a way that no light can come in from the backside of your mirror and into the booth.
2. Make sure no light is coming in from any other direction to the inside of the booth (for example, the hole at the top of the booth, where the wires connected to the flash are going through).
3. Make sure your camera's built-in flash is disabled.
4. Try to tilt your camera a little bit down.
5. Tilt your flash \ umbrella a little bit up. If that didn’t help, try to face the flash to the front (so it faces the people in front of the booth).
6. Try to disable the flash and increase the ISO on the camera to test if it’s the flash causing it.
7. Make sure there is no direct light pointing at the screen. Change the position of your booth if needed (there might be something bright in the background that bumps the light back to the screen).
8. If you have any LED lights inside the booth (the TV’s for example), try to cover it with a black tape strip.
9. If the above doesn't help, cover the white text on the inner side of your camera's lens (you can cover it with a black marker or a duct tape).
10. If the issue is your LED ring light reflection: Make sure you have a LED Ring Stop Ring Feature state before the DSLR feature state: