Last poster information not being properly updated when topics are moved

Some weeks ago it was noted on phpbb.com that the last poster in General Discussion was set to t_backoff when in fact she was not. The originating topic was:
http://www.phpbb.com/community/viewtopic.php?f=64&t=2147441
As can be seen in not_t_backoff.png and t_backoff_not_last_poster.png, the last poster was actually drathbun. There are likely two possibilities here:
1. Somehow the last poster for the forum was set to t_backoff when she moved the topic or (more likely)
2. The shadow topic was updated with the last poster information after the topic was moved but the forum information was not updated, pressumably because only the forum the topic is in gets the last poster information updated.

Either the original forum should continue getting updated or the shadow topic should not continue to be updated with the latest poster information, if that is what is happening. Not really sure what should be the end result in this scenario except that t_backoff shouldn't have been listed as the last poster.