Failed to load resource: net::ERR_CONTENT_DECODING_FAILED office-JS

Question

I just created a new boilerplate Yo office Excel addin with React and typescript. It worked for a short time but than I got some strange errors:

My taskpane remains empty and I cannot find out why it does not work. What I tried so far:

1. Close the Node server and start again with "npm start"
2. "npm install" to make sure that all depencies where met.
3. Removed line by line the App code to find out if the error is related to a custom module

any help would be greatly appreciated,