when checking a parameter to override in a parameterized class definition, i get
PG::Error: ERROR: null value in column "updated_at" violates not-null constraint : UPDATE "lookup_keys" SET "default_value" = '--- /etc/prout2', "description" = '', "validator_type" = '', "updated_at" = NULL WHERE "lookup_keys"."id" = 1

full trace is
ActiveRecord::StatementInvalid
PG::Error: ERROR: null value in column "updated_at" violates not-null constraint : UPDATE "lookup_keys" SET "default_value" = '--- /etc/prout2', "description" = '', "validator_type" = '', "updated_at" = NULL WHERE "lookup_keys"."id" = 1
app/controllers/puppetclasses_controller.rb:52:in `update'
lib/foreman/thread_session.rb:31:in `clear_thread'

i also tried updating by SQL the value, but then i get an error when actually overriding the parameter within a host definition. in that case, i get
unknown attribute: managed_id

with this full trace

ActiveRecord::UnknownAttributeError
unknown attribute: managed_id
app/models/host/managed.rb:210:in `lookup_values_attributes='
app/models/host/managed.rb:200:in `each_value'
app/models/host/managed.rb:200:in `lookup_values_attributes='
app/controllers/hosts_controller.rb:106:in `update'
app/models/taxonomy.rb:48:in `no_taxonomy_scope'
app/models/taxonomy.rb:55:in `as_taxonomy'
lib/foreman/thread_session.rb:140:in `as_location'
app/models/taxonomy.rb:54:in `as_taxonomy'
lib/foreman/thread_session.rb:105:in `as_org'
app/models/taxonomy.rb:53:in `as_taxonomy'
app/models/taxonomy.rb:47:in `no_taxonomy_scope'
app/controllers/hosts_controller.rb:105:in `update'
lib/foreman/thread_session.rb:31:in `clear_thread'