Hello,
Thank you for clarifying. In such cases, it is recommended to use the Modify properties option to change the license assignments. Also, making the actions run asynchronously might cause issues as such actions do not wait for others. Lastly, as we understand, you are trying to block access for the user, but keep their mailbox to perform some tasks on it. The proper way in this case is to just convert the mailbox to shared. They do not require licensing. Finally, you will have something like the following (pay attention to the actions order):