复制自定义配置后Nginx Docker容器卡在启动就绪状态求助

问题背景 #

我尝试运行一个Docker容器，当Dockerfile中包含复制自定义Nginx配置的语句时，容器无法正常启动；但移除该语句后，容器可以正常运行。我已经确认Nginx配置文件语法检测通过，且尝试使用默认配置也存在问题，因此怀疑问题不在配置文件本身，求排查线索。

原Dockerfile（无法正常运行） #

FROM node:14-alpine AS builder
WORKDIR '/app'
COPY package.json .
RUN npm install
COPY . .
RUN npm run build

FROM nginxinc/nginx-unprivileged
COPY --from=builder /app/build /usr/share/nginx/html
COPY nginx.conf /etc/nginx/

修改后的Dockerfile（可正常运行） #

FROM node:14-alpine AS builder
WORKDIR '/app'
COPY package.json .
RUN npm install
COPY . .
RUN npm run build

FROM nginxinc/nginx-unprivileged
COPY --from=builder /app/build /usr/share/nginx/html

我的Nginx配置文件 #

pid /tmp/nginx.pid;

events {}

http {
    server {
        location /api {
            proxy_set_header Host $host;
            proxy_set_header Cookie $http_cookie;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "Upgrade";
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_http_version 1.1;

            proxy_pass http://#removed_for_privacy#;
        }

        location /socket.io/ {
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "Upgrade";
            proxy_set_header Host $host;
            proxy_pass #removed_for_privacy#;
        }

        location / {
            index  index.html;
            try_files $uri $uri/ /index.html;
        }
    }
}

Nginx配置语法检测结果 #

nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

请问对此有什么排查线索吗？

内容的提问来源于stack exchange，提问作者jvdutrag