I start recording, and it immediately ends with an error

I start recording a conference, it immediately ends with an error, but when I change the capture size from 1920x1080 to 644x644 and only the upper left piece is visible, everything is recorded without problems.
Please tell me what could be the problem?

Sounds like a capacity issue. What are the specs of your Jibri server?
If you change the resolution in jibri.conf, you need to change it in xorg-video-dummy.conf as well. Then restart both jibri and xorg.