Update: Solved it. I submited it to Beta Review from command line using fastlane/spaceship and it worked
When I try to re-submit a newer build for external-beta review (Tried with both "Have you made any significant changes" Off and On"), I get an error:
Beta App Description is required.
end ngRepeat: error in submitForReviewData.sectionErrorKeys track by $index
Feedback emails must be in the format: contact@example.com.
end ngRepeat: error in submitForReviewData.sectionErrorKeys track by $index
Feedback emails are required.
end ngRepeat: error in submitForReviewData.sectionErrorKeys track by $index
Marketing URLs are required.
All of the fields mentioned in the error are vaild and were not even changed since the last build which was approved before.
Does anyone know what is wrong and/or what I could do to fix it?