Affinity Publisher has a preview mode, which shows how the document will look when it is printed out. In this mode, all non-printing visual indicators are suppressed.
However, since 1.8.3. this mode is not respected for empty picture frames when zooming out.
Example:
Here is my masterpiece. In it, I want green and grey backgrounds and so have used empty picture frames to create this. In preview mode, it looks like how it will print out.
However, if I zoom out too much, the visual indicators for empty picture frames appear, even though preview mode is still active. Converting the picture frames to curves does not help (although the issue will go away if the frames are converted to text frames).