InDesign: Objects from Masterpages can’t be deleted locally

I'm having the same problem. Did you ever find a solution?

I’ve been seeing other posts describing the same problem.

Does it happen if you Save As to IDML and then open the saved IDML? If that doesn’t work can you share the file?

Are you master pages based on a 'mother' Master page maybe? That said, also should not lead to the behaviour you see. Did you try the idml roundtrip?

I have not seen this as a problem. I am working with that InDesign version on a Mac with Mojave and have not run into the trouble that you describe. Have you tried resetting your InDesign preferences to make sure that there is no corruption in your copy of the program?

To do so on a Mac:

The User Library folder in which InDesign’s preferences are stored is hidden by default on most Macintoshes. To access it make sure that InDesign is closed and click on the desktop to launch a Finder Window (Command-N). With this window in column view follow the path User>Home folder (it’s the folder with an icon that looks like a house—it may have the user’s name rather than “Home”) and click on the Home folder. With the Option Key pressed choose Library from the Finder Go Menu. “Library” will now appear within the Home folder. Within the Library folder find the folder called Preferences and within it find the folder called “Adobe InDesign” and the file called “com.adobe.InDesign.plist” and delete both that folder and that file. When InDesign is next launched it will create new preference files and the program will be restored to its defaults.

The advantage of manually deleting preference files in this manner is that after you’ve reset up the program (make sure that no document window is open) to your liking, you can create copies of your personalized “mint” preference files (make sure that you quit the program before copying them—that finalizes your customization) and use them in the future to replace any corrupt versions you may need to delete.