Here is the trace:

ActiveRecord::StatementInvalid
PG::StringDataRightTruncation: ERROR: value too long for type character varying(255) : INSERT INTO "audits" ("action", "associated_id", "associated_name", "associated_type", "auditable_id", "auditable_name", "auditable_type", "audited_changes", "comment", "created_at", "remote_address", "user_id", "user_type", "username", "version") VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15) RETURNING "id"
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/hostgroups_controller.rb:64:in `update'
app/models/concerns/foreman/thread_session.rb:33:in `clear_thread'
lib/middleware/catch_json_parse_errors.rb:9:in `call'

I am attempting to update the parameters for a mysql hostgroup which does have a fairly long set of parameters. Let me know if you need further information.