The error "Name or service not known" (HTTP/500) is returned by the Red Hat 3scale 'backend-listener' pod

Issue

APIcast is returning HTTP/403 (Unauthorized) on every call. The 'backend-listener' pod is returning the following error message:

<YYYY>-<MM>-<DD>T<HH>:<MM>:<SS>.491373134Z 10.1.1.1, 10,1,1,2, 10.1.1.2 - - [<DATE> UTC] "GET /transactions/oauth_authrep.xml?service_token=<service token>&service_id=<service id>5&usage%5Bhits%5D=2&app_id=<app id> HTTP/1.1" 500 "Name or service not known" 0.001368853 - "rejection_reason_header=1&limit_headers=1&no_body=1"
<YYYY>-<MM>-<DD>T<HH>:<MM>:<SS>.491400828Z <DATE> +0000: Rack app error: #<RuntimeError: Name or service not known>
<YYYY>-<MM>-<DD>T<HH>:<MM>:<SS>.49140937Z /opt/ruby/3scale_backend-2.92.0/vendor/bundle/ruby/2.5.0/gems/redis-4.1.1/lib/redis/connection/hiredis.rb:19:in `connect'
...