Parallel Execution Node


I have some questions about the Parallel Execution nodes (KNIME Labs):

I have a node which spawns an external process, which I want to run in parallel. Each process need to have its own unique file path, so I pass a file path to the node using flow variables. I'm using the Java Edit Variable node to construct a flow variable with a path name based on the chunk number:
return "F:\\KnimeTemp\\Chunk" + Integer.toString($${Ichunk_index}$$);

(I have attached a screenshot of the workflow)

This approach works, but I have some questions:

1) I get the following warnings:
"WARN      Dock In MVD     Errors overwriting node settings with flow variables: Unknown variable "PATH""
"WARN      Java Edit Variable     No such variable "chunk_index" of type INTEGER"
But the variables (PATH and chunk_index) *are* set correctly. Why the warnings?

2) The chunk numbering seems strange. For instance, if I divide into two chunks, the 'chunk_index' flow variable is set to 0 and 2. However, if I 'Add Chunk Index to RowID', they are 0 and 1.

3) During execution, a new node (a container node called 'Parallel Chunks') appears, and then (sometimes) disappear. It is connected to the flow variable port. Is this the expected behavior? If you delete this node, the Parallel Chunk Start node will no longer work, and complains with a:
"ERROR     Parallel Chunk Start     Execute failed: No such node ID: 0:0:34:2"

4) If I choose to execute the 'Parallel Chunk Start' node, not all chunk are executed. It seems exactly *one*
 chunk is not executed: e.g. if I divide into three chunks, only two are executed (and the 'Dock In MVD' will never finish - though the mysterious 'Parallel Chunks' node will finish). If I instead execute the last node in the loop (the 'Dock In MVD' node), all chunks are executed and the loop finishes correctly.