Another effect related to this:

Warning!
Validation failed: Match fqdn=hostname.domain.com does not match an existing host

If you feel this is an error with Foreman itself, please open a new issue with Foreman ticketing system, You would probably need to attach the Full trace and relevant log entries.
ActiveRecord::RecordInvalid
Validation failed: Match fqdn=adam.cisco.com does not match an existing host
app/models/concerns/host_common.rb:46:in `block in lookup_values_attributes='
app/models/concerns/host_common.rb:39:in `each_value'
app/models/concerns/host_common.rb:39:in `lookup_values_attributes='
app/controllers/hosts_controller.rb:113:in `block in update'
app/models/taxonomy.rb:41:in `block in no_taxonomy_scope'
app/models/taxonomy.rb:48:in `block (2 levels) in as_taxonomy'
app/models/concerns/foreman/thread_session.rb:143:in `as_location'
app/models/taxonomy.rb:47:in `block in as_taxonomy'
app/models/concerns/foreman/thread_session.rb:108:in `as_org'
app/models/taxonomy.rb:46:in `as_taxonomy'
app/models/taxonomy.rb:40:in `no_taxonomy_scope'
app/controllers/hosts_controller.rb:105:in `update'
app/models/concerns/foreman/thread_session.rb:33:in `clear_thread'
lib/middleware/catch_json_parse_errors.rb:9:in `call'

I'm seeing that the name field is changing it's value from creation time, and the same for the domain dropdown.

Also, the IP should be constant in between edits (no need to overwrite with the same value)

Another related issue:

Changing the domain of an existing host results in:

xx has already been taken

This makes it impossible to save the node.

In 1.8.2 this has yet another side effect, causing node parameters to be blanked out

When creating a new host: host.domain.tld the name is actually set to: host.sub.domain.tld

I have both domain.tld and sub.domain.tld present.

root@foreman:~# sudo u puppet /etc/puppet/node.rb host.*domain.tld*
--
classes: {}
parameters:
puppetmaster: foreman
domainname: ''
root_pw:
foreman_env: production
ip:
mac:
foreman_subnets: []
foreman_interfaces:
- mac:
ip:
type: Interface
name: host.*sub.domain.tld*
attrs: {}
virtual: false
link: true
identifier:
managed: true
primary: true
provision: true
subnet:
environment: production

I am also unable to edit this host, as GUI reports: "name is already in use" when attempting to submit any changes