Our torque setup involves a default queue, which is a routing queue.
One of its destinations is a routing queue as well:

create queue default
set queue default queue_type = Route
set queue default route_destinations = atlas
set queue default route_destinations += dev

create queue dev
set queue dev queue_type = Route
set queue dev route_destinations = q1
set queue dev route_destinations += qs
set queue dev route_destinations += ql

(q1, qs, ql are execution queues).
When I submit a job, it always ends up in the dev queue, it never gets
delivered into one of the execution queues. As if routing of jobs is
tried once only (from default to dev).

The setup works without problems under torque-2.5.11.
As a consequence I have not been able to test torque-4.0.0 at all;
I cannot get a single job to run.