Karma tests only run half the time in Docker environment

Are there any known race conditions that happen when Karma is used with Docker? The test runs correctly _sometimes_. Example: I run karma start and the tests don't run correctly (shown below), but when I run it a second time, it might run correctly (also shown below).

### Expected behaviour
The tests run consistently every time the karma server is started with `./node_modules/karma/bin/karma start ./karma.conf.ts`. I am in a Docker environment.

### Actual behaviour
Sometimes, the tests run to completion correctly. Other times, the tests do not run at all.

When the tests run correctly:

When the tests don't run correctly:

### Environment Details

- Karma version (output of `karma --version`):
4.2.0
- Relevant part of your `karma.config.js` file