Firebeetle OSD Shield showing characters instead of transparent background

I'm working with the FireBeetle OSD Character Overlay Module with an Arduino Leonardo and using the DFRobot_OSD Arduino code. I'm able to get the example code running and the OSD module correctly adds the overlay text to the screen, however in the unused spaces it puts a character instead of a transparent background and I can't figure out how to fix it. Please let me know what I can do to correct this or if it's just a faulty module.

The image upload functions don't seem to be working so here's a link to an image of the OSD video output: https://imgur.com/PCvxQRg