multi datasource loops for the one datasource

I have set up a nested-branch in a multiple loop structure, but I am finding that the loops are acting eratically. Instead of diverting to the step specified, it falls through... executing all the other loops below.

This is how it looks:

datasource
branching groovy script

set parameter groovy
loop (1) to branch
request type 1
loop (2) to branch
request type 2
loop (3) to branch
request type 3
loop (4) to branch
END placeholder



Any advice? Is this a known bug?
How might you go about implementing this sort of structure?

Kind regards,

S