I'm sure that the accuracy change shown over your userbar is only when the hundredth place or bigger is changed. The accuracy change shown on the ranking screen after the song is most likely being rounded.
Basically, that just means if your accuracy improves by .001% from a song, and you had 95.999%, you will see +.01% on your userbar, since your accuracy would now be 96.00%. You would not see an increase of .01% on the ranking screen since your accuracy is not going up by .01%. (Anything in that paragraph is assuming accuracy is calculated a certain way. I don't actually know how accuracy is calculated that well.)
That being said, I'm sure peppy already knows what the issue is and will get around to this when he can.
Ticketed:
http://osu.sifterapp.com/projects/4151/ ... 6/comments