iOS Dock layout claims 'duplicate'?

Valued Contributor

I have a simple device profile using the Restrictions. I have allowed only two apps, one of them (Firefox) on page 1, and the second (Settings) on page 2.

When I try to add Firefox to the Dock, I get a message 'duplicate', and when saving the profile I get the message

"No Dock Layout

You have not added any content to the Dock. This will result in an empty Dock on each device."

This is not quite true, since I still get 'Settings' in the Dock, despite the fact it is not listed in the profile.

Any idea why I get a 'duplicate' message despite the fact that the app is not listed as being added to the dock?

I am puzzled by this behaviour. Just in case this matters: This is on JSS 10.15.1.