I tried all versions of Unreal and I didn’t get any such error.
Maybe rebuilding the project can solve your problem.
You might want to check out the video I made about adding video to . (Visual explanation)
It is not a webcam, but video material and broadcasting are created in the same way.
You may also want to take a look at the video set I prepared using UE4, NVIDIA, OBS, ZOOM and a few other programs. (Explanation in a different language, but visual narration available)
https://www.youtube.com/playlist?list=PL83GyhfD6TetNz6HTS2YFHPkVHk_H3nTo