Page content disappears upon opening in edit mode

Yesterday I went to edit a pre-exiting page on my 5.0.5 site, clicking on the edit button. Imagine my surprise when the page finishes opening in the tinymce editor and there is no content in the editor window! All content, text, table, lists and image were completely gone. This is completely repeatable. I opened in Tools/source code and this was it:

Needless to say I didn't save the changes. This problem doesn't happen on any other page. I can create new pages and no problem. However when I copy/paste the entire page, the resulting page has the same issue. Also, when I copied the content from the problematic page which was opened in .../view and paste it onto a newly created page, this new page will have the same disappearing content problem. I've checked error logs, nothing.

I've got lots of ways I can work around this problem but I thought it was something interesting to share. Any ideas?

I would not trust this view: while it is a perfect empty page, it does not justify the observation "opening in tinymce".

As you still see the correct content in the "view" view, the problem is local to the "edit" view.

I would start by analysing the requests involved in the "edit" view (I am using "Firefox"; there, I would use the network analysis to get information about the requests involved, their urls, request parameters and responses). You should be able to find out which request introduces the problem - and, in case all requests look correct, you could assume a "tinymce" problem.
Once the problematic request identified, I would start debugging it (preferably in an interactive Python session - i.e. in a "bin/client1 debug").

When you edit this page: does it say that it it is actually a normal page ? (It should say 'Edit Page' at the top of the page.
My guess is that it is actually empty, but the view 'shows something'.
For example, it could be a collections that list content, or just a 'placeholder' for diazo.

http://path/to/my/page/getLayout return 'document_view' ?

Thanks @dieter and @espenmn, both of your comments got me thinking about this from a more effective trouble-shooting perspective. I explored both perspectives, took many screen shots to show the process. And finally I hit upon a really basic, trial and error approach (good for someone who might now know the big picture of what's going on). Since I knew that I could create a fresh page w/out a problem, and I could copy the content from that page, paste it on a freshly-created page and replicate the problem, I wondered if it was some part of the content on that page.

If I hadn't been so tired I bet I would have found this quickly--won't tell you how long it took. But anyway, I finally isolated the problem to this:
<abbr class="glossarizer_replaced" title="better than the rest"><abbr class="glossarizer_replaced">best</abbr></abbr>

I've got the awesome add-on, collective.glossary, and that seems to be somehow involved. I tested this further by creating a fresh page, including a different vocabulary word in my glossary, and sure enough problem was reproduced. I'll file a bug report on the collective.glossary github page. Again, thanks for your support.

thanks for reporting this; let's continue talking about it in: