ExternalReference breaks when loaded from linked content.

I have the following project structure:


There is my platform project with the mgcb file, which references all the content in Content project. Since all content is in another project, it’s added as links:
/build:../../Monofoxe.Playground.Content/Content/Maps/Test.tmx;Maps/Test.tmx

I am using ExternalReference in my tmx processor. If I put tmx project in the same directory as Content.mgcb, everything works fine. But if it’s linked from the Content project, this happens:


For some reason the Content project path is appended to the reference. Actual grass_0.xnb location is:
bin\Debug\netcoreapp3.1\Content\Maps\Tilesets

Talked to Harry. Seems like a Monogame bug.