Kafo

Please provide more information to reproduce the bug, such attaching your answers file (with credentials redacted) and precisely how you created the answers file (commands, whether you used interactive mode).

Added generated foreman-answers.yaml

The HighLine string class isn't replaced in this entry, as it's inside an array:

foreman::plugin::memcache:
  hosts:
  - !ruby/string:HighLine::String |-
    V1d0ak5XRnNiRmhsUnpscFRUQTBkdz09
  expires_in: 86400
  namespace: foreman
  compress: true

#15111 only fixes instances where the value is a HighLine::String. The same probably applies to hashes.

As a workaround, run foreman-installer --foreman-plugin-memcache-hosts=example.com replacing example.com with the hostname of your memcached server. It should reset the stored value. Else, replace the section of the answers file above with:

foreman::plugin::memcache:
  hosts:
  - example.com
  expires_in: 86400
  namespace: foreman
  compress: true

Applied in changeset 3126b0f702fa682c823a01e74f3e839f4ab079f4.