This issue appears in Firefox

• "91.3"
• 91.5.1esr (64-Bit)
• 91.6.0esr (64-Bit)

The markers on the chart

• have the wrong order
• are not all on the top layer

Behaviour is as expected in Chrome 98.0.4758.82 (Official Build) (64-bit).

How to use

1. Checkout this repository.
2. Change directories so you are inside the project folder.
3. The first time you do this, you'll need to run npm install so that you have Typescript set up.
4. npm run build will compile the TypeScript source files.
5. npm start will start your server on port 3000.
6. Ctrl+c to shut off the server.

Credit

The toy server used in this example, including build chain and directory structure, is forked from the excellent https://github.com/aleph-naught2tog/ts_without_dependencies .