There are two possible reasons for receiving the "Unable to edit properties" error when trying to save metadata properties in AEM:

Insufficient Modify Permission: The user needs to haveModifypermissions for the folder or assets within the folder to be able to edit the metadata. Without this permission, changes to metadata cannot be saved.

Invalid Metadata Path: If a metadata property in the schema is mapped to an invalid JCR path, AEM will not be able to save the changes. The system requires valid paths in the JCR to store metadata properties correctly, and any invalid path will result in an error.

Option B, involving asset locking, would prevent editing altogether rather than giving an error during property saving. Option C, mapping two properties to the same path, would result in overwriting issues rather than an error about saving properties.

For more details, refer toAEM’s Metadata Schema documentationandpermissions management.