I was trying to add an unordered list into a text box (using the Source code edit) like so:
When I click "OK" it appears in the WYSIWYG window, but then hitting "Done" on that causes the entire box and the text within to disappear from existence. This error occurs on both a new text box and an already-existing text box.
I experienced this on Windows 7 64, Chrome version 44.0.2403.130 m. Lay Theme v 1.035 and Wordpress v 4.2.4
Will let you know if I see this in any other browser or on OS X!
Edit: also happens on Windows Firefox v37.0 and Mac OS X 10.10.3 Chrome v44.0.2403.130 (64-bit) --
However this error does not occur on OS X Safari 8.0.5 !
Well I just tried with Mac and Chrome. I think it's probably not related to the operating system. For me it works without the textbox disappearing. Oftentimes when the textbox disappears it means there was malformed markup in that textbox. Like a wrong " quotation mark somewhere, it's hard to say.
Can you replicate the problem and post the whole code that is in your textbox before it disappears?
I know for sure if you put a quotation mark into the code at the wrong place or when you write
class="hey"then that makes the content unreadable.