STS configured in multiple ARS not working (4378715)

There is a requirement to implement multiple Active Roles Admin service hosts in a standalone configuration. The first ARS Admin host STS has been successfully configured and works as expected, however the other ARS Admin service hosts ARS WI do not appear correctly configured, when trying to configure ARS WI to STS in a second ARS instance, in the  page with the RSTS Proxy and port-number, the following error appears:

Currently ARS WI RSTS implementation only works for one Active Roles Admin service.

Status:
The Active Roles product team has raised Enhancement Request #465538 to allow multiple Active Roles Admin service hosts to work with ARS WI STS authentication option. This enhancement will be evaluated by the Active Roles product team and product manager to include it in a future version of Active Roles.

Workaround:
Configure STS in the first ARS Admin service host, and any other ARS WI deployments make sure they connect to the first ARS Admin host with STS configured.

See the following KB article:
Modify Active Roles Web Interface Connection Settings