Live streaming to YouTube over HLS with FFMPEG

When I stream my FaceTime camera to YouTube over HLS, my video freezes every couple seconds. Which settings do I have wrong, or am missing?

ffmpeg \
-f avfoundation \
-framerate 30 \
-video_size 1920x1080 \
-pixel_format yuyv422 \
-probesize 10M \
-i "0:0" \
-c:v hevc_videotoolbox \
-b:v 4500K \
-tag:v hvc1 \
-c:a aac \
-method POST \
-f hls \
"https://a.upload.youtube.com/http_upload_hls?cid=STREAM_KEY&copy=0&file=index.m3u8"

I'm troubleshooting this with my FaceTime camera right now, but I plan on using a capture card with a 4K studio camera after I get this working