The "Find or upload an image" link does not work, and is should not be displayed, this is a bug.
However, you can enter an image URL in the "Image URL" box.
Joseph
If you are using the current version of Moodle (2.7) you can use the Restrict access settings of the Glossary to prevent it from being displayed, and the Random glossary block will still work.
Joseph
Example:

I don't understand your problem. In Moodle, a Lesson is not a "file", it's an activity.
Joseph
@Sam,
You are asking a different question in the Subject of your message and in the text of the Message itself.
Please rephrase your question.
Joseph
The editors are enabled, yes, but which one is being used (the one at the top)?
And again, are you having the problem of "not having the buttons back" only when editing a Lesson question or in all the other activities where the HTML editor is used? If so, then this is not a Lesson problem and I suggest posting to the General problems forum.
Please provide a screenshot displaying the problem.
Joseph