Hi all,
Welcome to the community and thanks for these reports, @torb and @lukasz2! (Thanks for your report too @rodyvansambeek. 
)
We’ve opened an incident for this and are working on a fix.
In the meantime, can you try this workaround: Instead of clicking on the “Configure monorepo” link (displayed on “repository A”, let’s say), click on “Setup a monorepo.” on the right of the “Analyze new project” page and then select the “repository A” in the list of repositories. That should bypass the problem.
HTH,
Ann