Bumped the build back to #27764 and had the same issue. But, when I created a new game, there was no problem, indicating that my specific game file has the issue, not the game itself. Hope that helps
Just today I started having this problem as well. build #28009 AMD Radeon 280X video card. I have no solar panels on cyclops. If I'm patient and swim out past the cyclops then fps is restored, but then when i swim closed to either it or a base, fps …
Figured it out, Logitech Gaming Software key-maps to my mouse buttons were interfering with key bindings in the Subnautica menu. Just needed to know what I was looking for. Thank you. you're right, it's a Unity issue I see every now and then.