Others have been finding this "bug" out recently also...and it's increased due to the changes GH.com made to their site last month.
In short, it recorded your old "One" score because it was in still in your recent performances list. The system doesn't know when you played the songs, it just knows what you played most recently. This has gotten "worse" lately because the new design includes your last 5 songs whereas the old design only had your last 3, thus the chances of you having a previously played song in the list has gone up by 2.
For more details you can read more in the thread we started about the topic prior...
http://www.morningtoast.com/forum/index.php?topic=168.0...the score system is doing what it's told to do and there's not much I can do to account for this "bug" without taking the whole thing down and doing an overhaul. I, like you, have only been playing GH3 sparingly recently and it really effects us because the recent list of played songs doesn't change very much.