In my platform Moodle 2.7.5 I have set as default text editor TinyMCE editor. When, for example, I want to create a new course and entered into the configuration of course, does not show me the text boxes to fill. This error also I have seen in answering something in a forum and I think in any other activity where you have to fill text boxes (labels, questionnaires ...)
I performed the test to change the default text editor to Atto, and I have no such problems in the text boxes. This text editor shows me correctly the text boxes.
TinyMCE version that is installed in Moodle 3.5.10 2.7.5 is (2014051202).