It seem to me that Logos is getting more "buggy" with each update. The latest bugs are affecting the sermon editor badly. Selecting text can make it act erratically, selecting unwanted paragraphs. Pretty awful.
However, the worst problem has only been happening for a couple of weeks, and appeared suddenly, so I suspect an update is the cause.
When deleting or inserting text, the cursor will move to the beginning of the line. It's possibly on lines which are numbered. Then the whole editor goes blank, including the menu bar and everything. Just the tab text remains.
If I close the tab down and reopen the sermon, everything's there.