Creating service AtoZ may result in conflicting frequency being used while ZtoA might not

Consider the following network.

[ROADM-A] -------- [ROADM-B] -------- [ROADM-C]

When setting up a service, the direction matters. Meaning, you may end up with conflicting frequencies depending on whether the service is created from A to B or vice versa.

Prerequisites

Before confirming this bug, there need to be a service (ServiceBC). e.g. between ROADM-B-SRG1 to ROADM-C using frequency 961 (as an example).

How to reproduce the bug

Setting up an additional service from A to ROADM-B-SRG1 will not produce the same result as setting up a service from ROADM-B-SRG1 to A.

1. Setup ServiceAB, e.g. ROADM-A to ROADM-B-SRG1. In this case, the same frequency as ServiceBC is used, i.e. 961. This is unexpected.
2. Delete ServiceAB. Now reverse the order by setting up ServiceBA; ROADM-B-SRG1 to ROADM-A. In this case the frequency 960 is used. This is the expected behaviour.