net::ERR_SSL_PROTOCOL_ERROR：React调用Spring Boot后端失败求助

我在Droplet上部署了React前端应用与Java Spring Boot后端应用，同时运行配置了SSL证书的Nginx服务器。目前前端无法调用后端，已尝试修改URL为域名、更换不同端口，也在前端调用和后端CorsRegistry中分别尝试了HTTP与HTTPS协议。由于前后端在同一Droplet上，本以为连接应该很简单，但实际遇到了很大困难。

public class WebConfig implements WebMvcConfigurer {
    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/**")
                .allowedOrigins("https://www.pligtlisten.dk", "http://localhost:3000")
                .allowedMethods("GET", "POST", "PUT", "DELETE")
                .allowCredentials(true);
    }
}

version: '3.8'
services:
  web:
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - "80:80"  
      - "443:443" 
    volumes:
      - /etc/letsencrypt/live/www.pligtlisten.dk/fullchain.pem:/etc/letsencrypt/live/www.pligtlisten.dk/fullchain.pem:ro
      - /etc/letsencrypt/live/www.pligtlisten.dk/privkey.pem:/etc/letsencrypt/live/www.pligtlisten.dk/privkey.pem:ro
    restart: unless-stopped

FROM node:18-alpine AS build
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
RUN npm run build

FROM nginx:alpine
COPY --from=build /app/build /usr/share/nginx/html
COPY nginx.conf /etc/nginx/conf.d/default.conf
EXPOSE 80
CMD ["nginx", "-g", "daemon off;"]

server {
    listen 80;
    server_name www.pligtlisten.dk pligtlisten.dk;
    return 301 https://www.pligtlisten.dk$request_uri;
}

server {
    listen 443 ssl;
    server_name www.pligtlisten.dk pligtlisten.dk;

    ssl_certificate /etc/letsencrypt/live/www.pligtlisten.dk/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/www.pligtlisten.dk/privkey.pem;
    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_prefer_server_ciphers on;
    ssl_ciphers EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH;
    add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;

    location / {
        root /usr/share/nginx/html;
        index index.html index.htm;
        try_files $uri $uri/ /index.html;
    }
}

export const BASE_URL = "https://161.35.196.6:8080";
export const GOOGLE_ACCOUNT_ENDPOINT = `${BASE_URL}/googleAccount`;
export const POINT_SCORE_ENDPOINT = `${BASE_URL}/pointScore`;

内容的提问来源于stack exchange，提问作者TheEagle