Docker compose - external links fail after successfull restart

Question

the situation is this: I have three different dockers compose files for three different projects: a frontend, a middleware, and a backend. FE is Ember, middleware and backend spring (boot). Which should not matter here though. Middleware uses an external_link to the backend, and frontend (UI) is using an external_link to middleware.

When I start with a clean docker (docker stop $(docker ps -aq), docker rm $(docker ps -aq)), everything works fine: I start the backend with docker-compose up, then middleware, then frontend. Everything is nice all external links do work (also running Cypress e2e tests on this setup - works fine).

Now, when I change something in the middleware, rebuild the image, stop the container (control+c) and restart it using docker-compose up, and then try to restart the frontend (control + c and then docker-compose up), docker will tell me:

Starting UI ... error

    ERROR: for UI  Cannot start service ui: Cannot link to a non running container: /32f2db8e96a1_middleware AS /ui/backend

    ERROR: for UI  Cannot start service ui: Cannot link to a non running container: /32f2db8e96a1_middleware AS /ui/backend
    ERROR: Encountered errors while bringing up the project.

Now what irritates me: where is the "32f2db8e96a1" coming from? The middleware container name is set to "middleware", which is also used in the external link of the UI, and works fine for every clean startup (meaning, using docker rm "-all" before). Also, docker ps shows me that a container for the middleware is actually running.

Unfortunately, I cannot post the compose files here, but I am willing to add any info needed.

Running on Docker version 18.09.0, build 4d60db4 Ubuntu 18.04.1 LTS

I would like to restart any of these containers without a broken external link. How do I achieve this?

Since you guys take time for me, I took time to clear out two of the compose. This is the UI/frontend one:

files:
version: '2.1'

services:

  ui:
    container_name: x-ui
    build:
      dockerfile: Dockerfile
      context: .
    image: "xxx/ui:latest"
    external_links:
      - "middleware:backend"
    ports:
      - "127.0.0.1:4200:80"
    network_mode: bridge

This is the middleware:

version: '2.1'

services:

  middleware:
    container_name: x-middleware
    image: xxx/middleware:latest
    build:
      dockerfile: src/main/docker/middleware/Dockerfile
      context: .
    ports:
      - "127.0.0.1:8080:8080"
      - "127.0.0.1:9003:9000"
    external_links:
      - "api"
    network_mode: "bridge"

The "api" one is essentially the same as middleware.

Please note: I removed volumes and environment. Also I renamed, so that the error message names will not fit perfectly. Please note the naming schema is the same: service name goes like "middleware", container name uses a prefix "x-middleware".