SYMPTOM:
An Administrator user is unable to edit a table when there is another user who is viewing Table with Read-only mode. For more information about expected behavior with concurrent schema object editing, refer to:
KB17418: ‘The schema is being modified by Administrator’ message appears when attempting to edit a schema object in MicroStrategy Developer9.4.x-10.x -
STEPS TO REPRODUCE:
Execute the following in Strategy Tutorial:

The schema is being modified by ViewOnlyUser. Do you want to open Table Editor as read-only?

Cannot unlock this object because the requested lock kind does not match that of the lock currently placed on the object.

* If the user who login to the project first had a privilege to edit the table object and chose to open the table in read-only mode, then, Administrator user logged in later from another Desktop Instance can edit the table without any issue.
CAUSE:
This is a known issue with Strategy Developer 9.x - 10.x.
ACTION:
Strategy is investigating this issue and will continue posting updates as soon as they become available.
WORKAROUND:
Revoke view access to schema objects from the users who does not need to edit them.