Error extracting metadata for project XXX: System.ArgumentException: An item with the same key has already been added.

[jplayer1978]

Operation System: (Windows or Linux or MacOS)
Windows 10 Pro

DocFX Version Used:
2.40.12

Template used: (default or statictoc or contain custom template)
Default

Steps to Reproduce:

1. Include single project in docfx.json
2. Build docfx project
3. receive error --> Error extracting metadata for project XXX: System.ArgumentException: An item with the same key has already been added.

Expected Behavior:
Documentation to be built.

Actual Behavior:
Error extracting metadata for project XXX: System.ArgumentException: An item with the same key has already been added.
Documentation is not built.

ADDITIONAL COMMENTS
If I target a different project it will work however there are 3 or 4 projects within this solution that exhibit this same issue. I have looked for duplicate references and many other items and cannot find anything glaring that should cause this issue.

Thanks for your assistance.

[superyyrrzz]

Could you provide a sample repo to help reproduce the issue?

This ma be related to #1414 #2532 #3778 , while I think #1420 should already fix this.

[jplayer1978]

I am unable to share the project, I could share a csproj file if that would be helpful.. I have also checked for duplicate refs and pretty much anything else that I could find about the issue online. Are there any other recommendations?

[superyyrrzz]

A log containing error call stack may be helpful.

[ElanHasson]

See #2532 (comment)

[superyyrrzz]

dupe of #2532