Defender plug in issue

Hi, this website is having an issue with defender. It flags up a report that says "You 6 files needing urgent attention!". Then beneath that warning it says "Wordpress Core Integrity - 6 issues" then a button that says "Fix Issue". When I click the button it loads another page that says "Your server resource usage is too close to your limit. Please try again in 15 minutes." It does this no matter what time of day I try it. It also gives the same error if I try to "Run New Scan". I don't see how the server resource can be too close to it's limit though, as I have a number of wordpress installs for different domains on the same server. All of them are purring along like a troupe of kittens. Can you point me in the right direction please? Maybe at least to the 6 files that have an issue please?