The V-600UHD's SDI output is only capable of 50 and 59.94 frame rates. HDMI has additional options.
If you want to output a 30 Hz frame rate via HDMI, you will need to choose 3840x2160 or 4096x2160 in the Processing menu:
Menu > System > Processing > Format > 3840x2160 or 4096x2160
The 1920x1080 setting will not work for this, you will need to choose 3840x2160 and down-convert the output separately. The 4096x2160 setting cannot be down-converted.
Next, return to the System menu, and change the Frame Rate setting:
Menu > System > Frame Rate > 30 Hz
If you want to output 1920x1080 HD instead of 3840x2160 UHD, change the following setting:
Menu > Output > HDMI Out X > Down Converter > Enabled
The outputs are down-converted individually, so you can have a mix of HD and UHD HDMI outputs.
A System Format of 1920x1080, 3840x2160, or 4096x2160 will disable SDI output. More information is in this guide:
If you do not see some of these options, update your firmware to the latest version: