I've got a weird inttermitent problem that has effected multiple sites. Blocks disappear en masse for site/school administrators when logged in. Guest users and pupils logged in can see the blocks without problem.
Looking through the HTML source I can see that the blocks are being output by the PHP code. However, something is causing the CSS to render them in such a way that they're not visible. I don't think a display:none rule is being applied, because the length of the page is effected, i.e. they're being shunted below the main content. Something is happening to the margins or padding of content to effect the positioning, and therefore the whether you can see them or not.
I went through the logs for a site for the period before this happened on one of the sites. I wanted to see if a user had changed a setting inadvertently. But the only interactions were views or edits to courses. No changes were made to any of the administration pages. Also, I'm not aware of a setting that would hide blocks only for administrators.
Nobody has edited the core or theme CSS files for these sites, as I'm the only person (other than server admin) with access to the files.
This issue has occurred before on different sites, but has 'magically' resolved itself a week or so later.
Has anybody else encountered (and hopefully resolved) this, or a similar, issue?
I have logged this as a bug. You can find the bug report at https://tracker.moodle.org/browse/MDL-37486
For the benefit of the developers fixing this, I have attached some screenshots of an effected site.
This is the site with the bug in action
This is the site as it should be rendered
To the best of my knowledge (and from looking at the site) only two accounts add site news to the front page, one of which is the site admin account. Several people have access to the site admin account, though I'm certain none of them copy from Word. I don't think the other account user copies HTML from Word either from looking at the code, I will attempt to find out from that user what they do.
Problem solved, here is the fix:
DO NOT COPY/PASTE CONTENT DIRECT FROM WORD OR OUTLOOK INTO MOODLE!
Copy/paste from Word/Outlook retains HTML formatting, this will break your layout. Instead use the paste text only button, this removes Word/Outlook HTML formatting (see attached image where the button is highlighted).
For a further discussion of problems caused by Word/Outlook HTML formatting see this thread: https://moodle.org/mod/forum/discuss.php?d=143900
Many thanks to Mary Evans for diagnosing this user error issue.