Under the curtains, the app uses programming interface provided by Confluence. It is known to trigger defects sometimes.
When selected to copy properties, a Confluence bug may be triggered that causes significant slow down of page tree copy process, and it can generate multiple copies of the page tree.
It is recommended to disable properties copy option in case you experience such defect.
Once you copied the page tree and want to edit one of the copied pages you might see the error:
This is Atlassian Confluence error: CONFCLOUD-70325. Please visit the ticket's page and click the Affected customers field to let Atlassian know that this issue affects your team work.
Meanwhile, we offer some workarounds:
2. Open "Unpublished changes" dialog