I tried using an anki plugin (https://ankiweb.net/shared/info/932119536) to display the pitch accent of words I'm learning. Some of the words I tried entering showed multiple possibilities for the same word. For example, it shows that 二つ rises on た, but may or may not drop on つ. Its the same with 三つ. 夜間 can either start high and drop after や, or rise on か.
I am looking for the "officially correct" accent of Tokyo Japanese. I saw an official pitch-accent book by NHK somewhere.
So my question is, do some words really have more than one possible accent? I know the accent can be modified for any word by the situation, emotion, etc., but will an official pitch-accent dictionary list multiple accents. The plugin I used does it automatically (although it claims they originated from NHK) so I'm worried there could be errors.