FFmpeg SVT-HEVC stress test failed

[hanbing001]

When I use FFmpeg SVT-HEVC for stress test, there will be some channels "Conversion failed".
Reduce to 40 channels will be OK.
Server Configure:
Intel(R) Xeon(R) Platinum 8470N
Total online memory: 256G

for((i=1;i<=56;i++)); do
ffmpeg -i Ghost_Towns_1080p_8bit_420_30fps.h265 -c:v libsvt_hevc -preset 9 -profile:v 1 -rc 1 -g 119 -sc_detection 0 -b:v 5M -maxrate 10M -bufsize 20M -y out/${type}${preset}1080p"${i}".h265 2>&1 |tee log/test_1080p${type}${preset}${profile}_"${i}".log &
done

[vost#0:0/libsvt_hevc @ 0x1228a40] Error initializing output stream: te= -0.0kbits/s speed=N/A
[vost#0:0/libsvt_hevc @ 0x2332a40] Error initializing output stream: te= -0.0kbits/s speed=N/A
frame= 1000 fps= 60 q=-0.0 Lsize= 20155kB time=00:00:33.06 bitrate=4993.2kbits/s speed=1.98x
video:20155kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000%
Conversion failed!2 q=-0.0 size= 1024kB time=00:00:02.10 bitrate=3994.6kbits/s speed=0.126x
frame= 1000 fps= 59 q=-0.0 Lsize= 20171kB time=00:00:33.06 bitrate=4997.2kbits/s speed=1.93x
video:20171kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000%
Conversion failed!8 q=-0.0 size= 16640kB time=00:00:27.06 bitrate=5036.3kbits/s speed=1.58x
frame= 1000 fps= 58 q=-0.0 Lsize= 20151kB time=00:00:33.06 bitrate=4992.3kbits/s speed=1.92x
video:20151kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000%
frame= 1000 fps= 56 q=-0.0 Lsize= 20141kB time=00:00:33.06 bitrate=4989.7kbits/s speed=1.86x
video:20141kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000%
frame= 1000 fps= 56 q=-0.0 Lsize= 20162kB time=00:00:33.06 bitrate=4995.0kbits/s speed=1.84x
video:20162kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000%
Conversion failed!0 q=0.0 size= 0kB time=-577014:32:22.77 bitrate= -0.0kbits/s speed=N/A
frame= 1000 fps= 55 q=-0.0 Lsize= 20231kB time=00:00:33.06 bitrate=5012.2kbits/s speed=1.81x

[hanbing001]

MobaXterm_172.16.113.139SPR_20230407_161229.txt