Hansen's experimentally proved five components of H_alpha line. Sommerfeld's relativistic correction was able to show only three components theoretically.
Dirac took into account spin orbit interaction and applied quantum mechanical relativistic correction and showed five components.
Yet there were discrepancies in Dirac's hydrogen fine structure.
One of them which I am familiar with is that states with same j and n values were taken as degenerate while they are not ( separation between such energy levels named as lamb shift).
What are the other discrepancies of Dirac's hydrogen fine structure?