static int mov_auto_flush_fragment(AVFormatContext *s, int force)
{
    MOVMuxContext *mov = s->priv_data;
    int had_moov = mov->moov_written;
    int ret = mov_flush_fragment(s, force);
    if (ret < 0)
        return ret;
    if (!had_moov && mov->flags & FF_MOV_FLAG_DELAY_MOOV)
        ret = mov_flush_fragment(s, force);
    return ret;
}

The product divides a value by zero.