Minitest fixture referencing incorrect objects

Question

class Document < ApplicationRecord
  
  belongs_to :individual, optional: true
  belongs_to :union, optional: true

  has_one_attached :file

Upon executing a test patch document_url(documents(:one)), params: { document: { title: documents(:two).title } }, xhr: true an error is returned:

ActiveRecord::RecordNotFound: Couldn't find Individual with 'id'=498572325
    app/controllers/documents_controller.rb:42:in `update'

the controller searches for the document's owner to generate an instance variable @individual = Individual.find(@document.individual_id). A putsin the controller returns consistent with the error @document.individual_id 498572325

The fixtures for documents.yml are

one:
  title: MyString1
  synopsis: MyString1
  individual: individuals(:one)

two:
  title: MyString2
  synopsis: MyString3
  union: unions(:one)

while individuals.yml does not establish a fixed ID, leaving it to the testing environment

one:
  shop: shops(:one)
  categoryminor: categoryminors(:one)
  union: unions(:one)
  name_last: MyString1
  name_first: MyString1

in the test, before calling the update action, we verify the value of the individuals(:one).id before logging in a user and get

puts individuals(:one).id
==> 980190962
puts documents(:one).individual_id
==> 498572325

So the test result is coherent. 'individual' is not to my knowledge a reserved word.

Why are the test data then shifting? Is this somehow related to Document class using ActiveStorage?