Can't play video file to virtual camera and then webcam to virtual camera v4l2

When I try to play a video to a virtual camera it works but when I try to play webcam to virtual camera it doesn't do anything.

What I do:

Playing video to virtual camera:

ffmpeg -re -i "yt.mkv" -map 0:v -f v4l2 "/dev/video2" and then ^C

Playing webcam to virtual camera:

ffmpeg -i "/dev/video0" -map 0:v -f v4l2 "/dev/video2"

What happens when I do last command: nothing. The last frame of the played video just stays there, frozen.

when i use ffplay /dev/video2 it outputs this:

[video4linux2,v4l2 @ 0x7fdcf4000b80] Dequeued v4l2 buffer contains 460800 bytes, but 1382400 were expected. Flags: 0x00000001.

i can play 2 different videos so i dont know why it isn't working

How do I get it to work?

why the downvote?