Error when creating extension with tfx: invalid part name

[urbanfi]

I was following this tutorial to create a custom azure pipeline task:
https://docs.microsoft.com/en-us/azure/devops/extend/develop/add-build-task?view=azure-devops#createpublisher

I always get the following error message when creating the extension:
PS C:\buildandrealeasetaskhome> tfx extension create --manifest-globs vss-extension.json

error: Error: Part Name '../buildAndReleaseTask/index.js' is invalid. Please check the following: error: 1. No whitespace or any of these characters: #^[]<>? error: 2. Cannot end with a period. error: 3. No percent-encoded / or \ characters. Additionally, % must be followed by two hex characters.

I can't find any problems in the filename itself.
I'm using windows powershell on Windows 10 Home.
tfx is Version 0.9.3

I attached the output of --trace-level debug
tfxdebug.txt

[urbanfi]

I found the following workaround:

This error only occurs when using sibling directories:
e.g C:\buildandrealeasetaskhome <-- containing css-extension.json
and C:\buildandrealeasetask <-- containing the extension

When using a parent-child structure this error does not occur
C:\buildandrealeasetaskhome\buildandrealeasetask