I have a problem. When I change the scenes or start OBS, it often happens that the camera is not displayed. Is this because of OBS or Elgato Cam Link or because I have a webcam and a camera connected to the PC?
OBS Studio creates a log file each time you run it which contains very useful diagnostic information. Without a log file, it's much harder for any support volunteers to figure out problems and your post may be ignored. To upload a log file, go to the Help menu > Log Files > Upload Last Log...
you have four instances of video devices of type "Live Streamer Cam 513" (at once!) and one Elgato Camlink.
You should know that each instance is concurrently fighting with the others. Whichever opens the cameras driver first, does win.
If you have just one camera of this type, you should clear all the instances, then:
1. Insert the first instance into the first scene you want it to;
2. on all subsequent scenes you want to use those cam: Insert it as "open existing" and target OBS to the first (and only) existing instance!
The problem is the instances you have set up in OBS. As long as you can distinguish the cams from each other, all is fine. For instance if you use the Sony by the camlink. Just follow the steps described above.
You can have as much physical cameras as your USB (and i/o subsystem) on your machine is capable for.