Can the question Something went wrong while saving this configuration: Area is already set be reopened? As it is currently closed as unclear.
The question is about a bug that occurs in Magento 2.2.4 and Magento 2.2.5. The workaround in the accepted answer solves the issue by suggesting to apply an official patch.
The existence of an official patch should validate the fact that the question is actually clear and doesn't need any more details (The numbers of votes and views on the question and the answer are more proof that the question is clear in my opinion).
Disclaimer: I slightly edited the post to make it even a bit clearer.