In a nutshell, I have two YAML files.
Although decoration shows error of parsing YAML, new provider is still sent in event. This is causing further processing which messes up the current config.
Stack trace: stackTrace
Light module to reproduce the issue: light-modules.zip
This is a related issue. Firstly, the endpoint worked with list syntax ( - ).
After deleting the decoration module, the endpoint stopped working.
Modifying the main YAML file made it work again.