ffmpeg transcoding randomly hangs with SVT-HEVC encoder

[Austin-Hu]

When repeat running the 2 ffmpeg commands below, the ffmpeg transoding randomly hangs:

    ./ffmpeg -i CSGO_SVT-HEVC.mp4 -c:v libsvt_hevc -rc 1 -preset 4 -b:v 4.4M -maxrate 4.4M -bufsize 8.8M -r 60 -g 120 -y 1080P.mp4
    ./ffmpeg -i ToS_2160p_59.94fps_2min.mp4 -c:v libsvt_hevc -rc 1  -preset 5 -b:v 9.6M -maxrate 9.6M -bufsize 19.2M -y -r 60 -g 60 -sc_detection 0 4k.mp4

The video clips are here. The issue could be reproduced with the SVT-HEVC commit of master branch, and the v4.2 branch of ffmpeg plus SVT-HEVC plugin. And need to find the pattern to simplify the reproducing steps.