I ran recently W3C link checker and noticed:
Processing http:List of broken links
Fragments listed are broken. See the table below to know what action to take.
Code Occurrences What to do
200 1 There are broken fragments which must be fixed.
http: What to do: There are broken fragments which must be fixed.
Response status code: 200
Response message: OK
Lines: 142, 261
Broken fragments and their line numbers: They need to be fixed!
Basically this means that the Chages Report refers to user id anchors which are never created.
These anchors should be created as invisible anchors right before the user id.