In studio when you hit Play mode or start a test server, if you tap the right mouse button you’ll notice that it is using the Camera Toggle. The issue is in the “in-game” settings, it’s set to Default (Classic).
Workaround is to go in the game settings and switch it to “Classic” each time. Seems studio doesn’t consider “Classic” the default, even though it says it would.
A similar issue happens with vehicle seat cameras. You need to reset the camera to get shift lock working in a vehicle seat. Doing this fixes it, but it happens every time you rejoin.