XDebug not breaking (VS Code / Docker / PHP)

I am going slowly crazy! I have had VS Code set to debug a WordPress plugin that I am developing in a Docker container. Importantly, this was working - but today it's utterly failed i.e. breakpoints are ignored. Obviously something changed but I have spent too long trying to figure this out, so reaching out for help now.

I have XDebug configured in the container and on the host, the PHP Debug and Docker extensions, etc. "php -v" reports what I would expect. I have the launch.json below.

Let me start with the suspicious part and see where this leads. The IDE reports the following - "Matches multiple schemas when only one must validate." Where can I / should I look to resolve this (what you see below is the entire file)?

I should add that the use of the absolute path is intentional. I spent a long time trying to get this to work with ${workspaceFolder} without luck but then - against some advice I read somewhere - I decided to use the absolute path and everything was working just fine (for a couple of weeks). Until it wasn't...

Thanks in advance.

{
"version": "0.2.0",
"configurations": [
    {
        "name": "Xdebug for Docker",
        "type": "php",
        "request": "launch",
        "port": 9000,
        "pathMappings": {"/var/www/html": "f:/docker/apps/wp1/html" }
    }
]

}