Saving or deleting image files results in an ExternalChangesException: Unable to save changes to unreconciled page null

Problem

Saving or deleting image files fails and results in the following exception in the log:

com.atlassian.confluence.pages.exceptions.ExternalChangesException: Unable to save changes to unreconciled page null
at com.atlassian.confluence.internal.content.collab.DefaultContentReconciliationManager.reconcileIfNeeded(DefaultContentReconciliationManager.java:149)

This affects operations with image files within the apps:

• Linchpin User Profiles
• Linchpin Events
• Linchpin Theme (bundeled with the app Linchpin Essentials or Linchpin Intranet Suite)

In particular, the following functions in these apps are affected:

Linchpin User Profiles

• Profile picture and profile background cannot be saved or deleted.

• LDAP Sync:

  • Profile picture cannot be saved.

  • Old profile picture cannot be deleted. Exception leads to abort and rollback of the complete LDAP sync, therefore the LDAP sync generally does not work anymore and no profile data is updated.

Linchpin Events

• Background image cannot be saved or deleted.

Linchpin Theme

• Background image and logo cannot be saved or deleted.

Diagnosis

Environment

The Confluence version installed is one of the following:

• 7.4.9 to 7.4.15

• 7.11.3 to 7.11.6

• 7.12.1 to  7.12.5

• 7.13.0 to 7.13.4

• 7.14.0 to 7.14.2

• 7.15.0 to 7.15.1
• 7.16.0 to 7.16.1

Cause

This is a bug in Confluence:

• [CONFSERVER-74671] Functions that rely on methods to work with files and attachments (including images) are failing after collaborative editing is disabled

Workaround

n/a

Resolution

Update Confluence to one of these fixed versions:

• 7.17.0 or higher
• 7.16.2 or higher patch-version
• LTS 7.13.5 or higher patch-version
• LTS 7.4.16 or higher patch-version