It should be noted that this issue does not occur if you were to create a new "test widget" (by dragging it from the widget list) every time instead of copying and pasting an existing widget.
The issue occurs in both 4.20.3 (CL 4369336) and 4.21.0 (CL 4541578).
Result: Only one of the "test widgets" in the "bugged widget" will have its text updated.
Expected result: All widgets will have their text updated.
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-66314 in the post.