I have OctoPrint 1.4.2 installed on PC and the Anet A8 3D printer connected via USB. Printer have Marlin firmware. In the timelapse settings I configured the timelapse snapshot URL and clicking Test show correctly the image from the camera. After printing finished i saw this error in OctoPrint web interface:
Rendering of timelapse CFFFP_stering_adj_v3_20210102160456 failed with return code -4
And in the octoprint.log I found:
2021-01-02 16:20:00,244 - octoprint.timelapse - WARNING - Could not render movie, got return code -4: 
I also check the path for ffmpeg and it was correct(clicking on Test shows that path is valid).
Thanks for any help