One major cause of seeing most of your clips as a Black Screen is an issue related to using a 4k camera and attempting to record in the wrong format.
NOTE: This issue will only occur when attempting to record to the camera's SD card when the recording format is set to the 4k format. If you do not record onto the camera itself, the black screen issue will not occur.
1. Use the touchscreen to access the menu
2. Select Image Quality/Size
3. Select File Format
4. Ensure the camera is set to AVCHD and not XAVC
Exit the menu
If it says completed you should be good to go!
This reduces the recording quality from 4K (3840 x 2160) down to 1080p (1920 x 1080)
As far as we've found, no 4k camera is capable of recording in 4k while simultaneously outputting an HDMI feed of any kind, making that resolution incompatible with all known replay systems.