WITH RECURSIVE doesn't work properly for me

I use following command to get a shortest-path query:

with recursive paths( src_id, dest_id, dist) as(

        select n1,n2,1

        from nodes

        union

        select src_id, dest_id, min(dist) 

        from (  select paths.src_id as src_id, nodes.n2 as dest_id, paths.dist+1 as dist

            from paths, nodes

            where paths.dest_id=nodes.n1

            and paths.src_id<>nodes.n2

            ) as Temp

        group by src_id, dest_id

        )

select paths.src_id, paths.dest_id, min(dist)

    from paths

    group by 1,2;

It seems that this query goes into infinite loops and finally run out of disk space. However, I testrf every iteration seperately and found that it will converge after 3-4 iterations. I wonder where is the problem. Could anyone help with it? The attatchment is the test data.

Thank you very much:)