Path not found error from 'update all content'. This message seems unrelated to the problem

Use Case 1:
As described in CMS7-3620 I wanted to import an XML file containing a namespace with bug fixes. I did not delete the old namespace node, but moved it to /content/documents/old/ in order to be able to put it back in case of failure. 'Update all content' went wrong, because namespaces are searched based on node type.
I got the following error message:
javax.jcr.PathNotFoundException: /content/documents/docs/cms/about/system requirements/system requirements/docs:section/docs:one_step

At first, I thought that that document may be corrupt, so I tested again, but this time deleted that document before 'update all content'. Now I got the same error message, but for the next document:
javax.jcr.PathNotFoundException: /content/documents/docs/cms/about/version_numbers/version_numbers/docs:section

The system requirements document was not the first document of the content.

Use case 2:
When I tried another time and deleted the namespace node before importing the bug fixed 'version', 'update all content' was successful, so there was no error with those documents.

Use case 3:
The newest content from the docsite fails on 'update all content', as described in CMS7-3616. It also gives the error message:
javax.jcr.PathNotFoundException: /content/documents/docs/cms/about/system requirements/system requirements/docs:section/docs:one_step