Regarding vehicles k=8 and k=9, the behavior you described is a result of the WHERE= clause in the CREATE DATA statement:
create data solution_data (where=(x1<>x2 and y1<>y2)) from [i j k]=
Some of your nodes (like 924, 925, and 926) have identical coordinates, and the WHERE= clause omits any arcs between such pairs of co-located nodes. Just remove the WHERE= clause, and you will see the expected arcs in the resulting output data set.
For the other question about decrementing flow instead of incrementing it, please start a new post.
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