#APL 25#

    1↓¨(1,∨⌿<\2=+\∘.=⍨a)⊂1,a←

Example:

    ]display 1↓¨(1,∨⌿<\2=+\∘.=⍨a)⊂1,a←2 1 1 2 3 2 2 4 5 6 7 3 7 0 5
    ┌→──────────────────────────────────────┐
    │ ┌→──┐ ┌⊖┐ ┌→────────────┐ ┌⊖┐ ┌→┐ ┌⊖┐ │
    │ │2 1│ │0│ │3 2 2 4 5 6 7│ │0│ │0│ │0│ │
    │ └~──┘ └~┘ └~────────────┘ └~┘ └~┘ └~┘ │
    └∊──────────────────────────────────────┘


***Old One:***

    {1↓¨(1,(⍳⍴⍵)∊,{1↑1↓⍵}⌸⍵)⊂1,⍵}

This is a nice question for the key operator (⌸) which was introduced with Dyalog APL v14.
It takes the left argument function ({1↑1↓⍵}) and gives it for each unique argument, the indices in the vector for that argument.
Here I'm taking the second index, then i check which of the indices is present in this list ((⍳⍴⍵)∊) and use the resulting boolean for splitting the original vector.

Can be tried online here:

[http://tryapl.org][1]


  [1]: http://tryapl.org/