KB39177: "Cannot save or move object 'System Hierarchy' with id 'XX' and type 'Hierarchy'. Its dependent object with id 'YY' and type 'Attribute' does not exist in the metadata." when working on more than one attribute in MicroStrategy Developer 9.4.x-10.

SYMPTOM:
When working on an attribute and without closing the editor window, and at the same time a new attribute is created by the same user, then attempting to save the first attribute will throw the error message seen in the screenshot below:

STEPS TO REPRODUCE:

1. Edit an existing attribute, modify one of the attribute form expressions.
2. Click 'Ok' to go back a screen, but leave the editor open.
3. Create a new attribute and leave this editor window open.
4. Go back to the editor window open in Step 2 and try to save and close.

CAUSE:
When a new attribute is created, an ID is generated even before the saves are changed, if we go back and try to save the attribute in the previous editor window, then this error message will be displayed because we are in the process of creating the attribute in the second editor window.
ACTION:
Editing multiple attributes at the same time is generally not a good practice, a lock is placed in the metadata so this will not happen if multiple users working at the same time, in this case the lock belongs to the user currently working in Desktop so he is able to encounter this scenario.
WORKAROUND:
Finish creating the attribute and close the newest editor window, then you can save your changes on the old editor window.