Errors started to point to the bundle

Question

For some reason, the error outputs for my React project now point to the bundle and not to my code:

Based on the linked post, I added the webpack.config.js file:

module.exports = {
    devtool: '#eval-source-map',
};

This did not help.

My .env:

GENERATE_SOURCEMAP=true
WATCHPACK_POLLING=true
CHOKIDAR_USEPOLLING=true

I actually do see my source files in the development tools:

So it seems that the source maps exist, but are not used for some reason.

What could have gone wrong and how do I fix this?