Let $A = \overline{\bigcup A_n}$, $B = \overline{\bigcup B_n}$ be AF algebras with the same Bratelli diagram. Then there is an isomorphism $\phi : A \rightarrow B$.
Let $x \in \bigcup A_n$ (say, $x \in A_k$ for some $k$). Is it always the case that $\phi(x) \in \bigcup B_n$ ?