感谢Ivan在此问题上为我指明了正确的方向。
Docker容器内的解析器应使用ipv6指令关闭的127.0.0.11上的Docker嵌入式DNS服务器：
server { listen 8443 ssl; server_name domain.com www.domain.com; index index.php index.html; root /var/www/base/public; location ~ ^/api/(.*)$ { resolver 127.0.0.11 ipv6=off; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header X-Forwarded-Proto $scheme; proxy_pass https://api.domain.com/$1; }}
