Error: "Please check URL"

[dlmw]

I have the following Docker compose:

services:
  barcodebuddy:
    image: f0rc3/barcodebuddy:v1.8.1.8
    deploy:
      placement:
        constraints:
          - "node.labels.barcodebuddy==true"
    volumes:
      - barcodebuddy-config:/config
    networks:
      - reverse-proxy-network
      - grocy-network
    depends_on:
      - grocy-frontend
      - backend

  grocy-frontend:
    image: "grocy/frontend:v4.2.0"
    deploy:
      placement:
        constraints:
          - "node.labels.grocy-frontend==true"
    networks:
      - reverse-proxy-network
      - grocy-network
    depends_on:
      - backend

  backend:
    image: "grocy/backend:v4.2.0"
    deploy:
      placement:
        constraints:
          - "node.labels.grocy-backend==true"
    volumes:
      - backend-db:/var/www/data
    environment:
      GROCY_MODE: production
      GROCY_CULTURE: fr
    networks:
      - grocy-network

volumes:
  barcodebuddy-config:
  backend-db:

networks:
  reverse-proxy-network:
    external: true
  grocy-network:

And here's my relevant Caddyfile configuration:

grocy.mydomain.com {
    reverse_proxy grocy-frontend:8080
}

barcode.grocy.mydomain.com {
    reverse_proxy barcodebuddy:80
}

Whenever I scan something, I get the following toast: Error: Unknown error occurred. Please check URL.. In the Barcode Buddy settings, it reports that the connection to Grocy is successful. Going to https://grocy.mydomain.com/api gives me the Swagger UI, but going to https://grocy.mydomain.com/api/ (note the trailing slash) gives me a 404 with the following JSON:

{
  "error_message": "Not found.",
  "error_details": {
    "stack_trace": "#0 \/var\/www\/packages\/slim\/slim\/Slim\/Middleware\/RoutingMiddleware.php(44): Slim\\Middleware\\RoutingMiddleware->performRouting()\n#1 \/var\/www\/packages\/slim\/slim\/Slim\/MiddlewareDispatcher.php(121): Slim\\Middleware\\RoutingMiddleware->process()\n#2 \/var\/www\/packages\/slim\/slim\/Slim\/Middleware\/ErrorMiddleware.php(76): Psr\\Http\\Server\\RequestHandlerInterface@anonymous->handle()\n#3 \/var\/www\/packages\/slim\/slim\/Slim\/MiddlewareDispatcher.php(121): Slim\\Middleware\\ErrorMiddleware->process()\n#4 \/var\/www\/middleware\/CorsMiddleware.php(27): Psr\\Http\\Server\\RequestHandlerInterface@anonymous->handle()\n#5 \/var\/www\/packages\/slim\/slim\/Slim\/MiddlewareDispatcher.php(269): Grocy\\Middleware\\CorsMiddleware->__invoke()\n#6 \/var\/www\/packages\/slim\/slim\/Slim\/MiddlewareDispatcher.php(65): Psr\\Http\\Server\\RequestHandlerInterface@anonymous->handle()\n#7 \/var\/www\/packages\/slim\/slim\/Slim\/App.php(199): Slim\\MiddlewareDispatcher->handle()\n#8 \/var\/www\/packages\/slim\/slim\/Slim\/App.php(183): Slim\\App->handle()\n#9 \/var\/www\/app.php(112): Slim\\App->run()\n#10 \/var\/www\/public\/index.php(45): require_once('...')\n#11 {main}",
    "file": "\/var\/www\/packages\/slim\/slim\/Slim\/Middleware\/RoutingMiddleware.php",
    "line": 76
  }
}