Try try add this option at the end of your video options to increase the queue size:
-max_muxing_queue_size 1024
This worked for me, but you may need a higher value like 2048 or even 4096. I found out about this here:
https://discussion.mcebuddy2x.com/t/ffmpeg-bug-too-many-packets-buffered-for-output-stream/1148