I did a dry run of the file caption usability study on Friday, and unfortunately, the usability tester ran into an error saving the caption, which prevents me from releasing the usability study to the remaining participants.

However, there is some feedback from the test which is valuable for us, regardless of whether we are able to fix what's resulting in the error that prevents the system from saving captions, which I am detailing below.

Help text in the caption field: "No caption defined" is unclear. It didn't give enough of a clue that a caption should be entered into the field.
Suggested change: use this text: "Add a one-line explanation of what this file represents" (which is a shortened version of the entire UW text: "Add a one-line explanation of what this file represents, including only the most relevant information")

Save error text is unhelpful. "The file has failed" error message is unclear and inconsistent. The tester was unable to publish captions despite many efforts, and for most of the time testing, blamed herself and her keyboard settings because the error messaging was vague and didn't indicate it was a system error. If two captions are being added at once, only one field will display an error, not both. This inconsistency was very confusing to the tester.
What else can we use that's accurate but also gives more information to the user so they know it's not their fault, but the system's?