Some strange anomalies are reported on Japanese Wikipedia.

I am not sure if this is a bug in software or something else, so I am reporting it here first.

#1 Three users indicated that their edit records include edits they had never made - wrong attribution.

#2 One of those users reported that while he was editing, he "became" another user - he was logged on as another user. He could see email address, watchlist, etc. associated with that account. The account he was switched to was also among one of the three users mentioned in #1.

To be more specific, the following three users reported wrong attribution.

http://ja.wikipedia.org/wiki/%E5%88%A9%E7%94%A8%E8%80%85:Avanzare reported his edit record include edit(s) he never made.

http://ja.wikipedia.org/wiki/%E5%88%A9%E7%94%A8%E8%80%85:Trashwriter said that he had never made this edit: http://ja.wikipedia.org/w/index.php?title=%E4%B8%AD%E4%BA%AC%E9%AB%98%E7%AD%...

http://ja.wikipedia.org/wiki/%E5%88%A9%E7%94%A8%E8%80%85:Kunipoo said that he had never made this edit: http://ja.wikipedia.org/w/index.php?title=%E3%83%98%E3%82%A2%E3%83%8C%E3%83%...

Also, User:Trashwriter reported he once became User:Avanzare.

User:Kunipoo reported he once saw the user name displayed at the upper right corner became NNNN or NNNNN. He experienced other error messages and slow responce when this happened. (User:NNNN and User:NNNNN do exist in Japanese Wikipedia, although the former has only one edit and the latter none.)

Is this something that might occur in relation to server overload?

Best,

Tomos