Assistance required please;

I'm a member of a group mailbox.

Up untill two weeks ago, I was able to move created folders with nested
folders into other folders - eg, a project with nested folders when
completed would be relocated into the project completed folder.

Now when trying to drag a project folder with nested folders directly
or when right click and select move folder - get message similar or
same as "Cannot copy this folder as it may contain private items."

Does not get message when just moving single folder (no nesting)

Same for other members of this group mailbox, so not just limited to
me.

This is stumping my support team, so any direction appreciated - they
have validated all permissions are correct per user at exchange group
mailbox level.

TIA

Carl