Hello Chris. Sounds like a tricky one to duplicate, but the Edit command you use is like starting over with fresh text, there is no guarantee that the original text will be there. Sometimes the window might open as a new TTS session and sometimes the window will open with the last text used. We recommend for user's not to rely that the text will still be there, as this tool's function is to create the audio and alternate closed caption file, not to store the inputted text. All it takes is switching the voice to another choice and all the text in the Plain Text input box will be replaced with the default text.
A related feature is for direct editing of the closed caption file, select the audio file, then Audio > Properties > Add Captions. This brings up a different window than the one you mentioned. This is the actual file the closed captions are stored in. Clicking Edit opens your text editor and the captions file with the timings included. Of course, now you aren't editing the audio but refining the caption file.
