I recently (few days ago on 09, January 2021) updated my OBS to 26.1.1. I found that my Lumix GH3, which is connected through Blackmagic Ultrastudio SDI and a Blackmagic Design HDMI to SDI converter, cannot be used anymore. I have no choice but to uninstalled the OBS 26.1.1 and re-installed to the very old version (20.1.3) which I have been keeping the installer in my computer (Fortunately I have been keeping it). After re-installed the old very, my camera works again. I hope this problem can be fixed on the next update. Thank you.