Magento 2.3.0 - Migrated from 1.9.3.4 - Some attributes not updating on product save

Question

Having some weird trouble with a migrated M2 website. I've seen some resources on here, but they all don't seem to be showing the same symptoms.

Migrated a site using the Magento tool - all went well apart from an odd issue with the select attributes not functioning as expected.

If I update a migrated attribute (Say Attribute Value "A" to Value "B"), it will revert to "A" on save.

However, If I create a new product (non migrated) and do the same thing on the same attribute it updates as expected.

I've read that it may be an issue in the eav_attribute table.

For reference, this is one of the troublesome attributes (which were also migrated):

*************************** 1. row ***************************
   attribute_id: 595
 entity_type_id: 4
 attribute_code: type
attribute_model: NULL
  backend_model: NULL
   backend_type: int
  backend_table: NULL
 frontend_model: NULL
 frontend_input: select
 frontend_label: Type
 frontend_class: NULL
   source_model: Magento\Eav\Model\Entity\Attribute\Source\Table
    is_required: 0
is_user_defined: 1
  default_value:
      is_unique: 0
           note: NULL

Compare that to a test attribute I created after migration:

*************************** 1. row ***************************
   attribute_id: 1212
 entity_type_id: 4
 attribute_code: test_select_attribute
attribute_model: NULL
  backend_model: NULL
   backend_type: int
  backend_table: NULL
 frontend_model: NULL
 frontend_input: select
 frontend_label: Test Select Attribute
 frontend_class: NULL
   source_model: Magento\Eav\Model\Entity\Attribute\Source\Table
    is_required: 0
is_user_defined: 1
  default_value:
      is_unique: 0
           note: NULL

There's no difference in the set up, so the backend_model issues I've read about don't seem to apply here.

Other issues I've noticed:

In debug.log, there's a bunch of these errors:

main.WARNING: Attempt to load value of nonexistent EAV attribute '575' 
                        for entity type 'Magento\Catalog\Api\Data\CategoryInterface'. [] []

Also, I can't for the life of me get these attributes to load in layered navigation. I would assume it's related to the above issues.

Anyone out there who's able to help at all?

Cheers

** EDIT ***

It appears that if that test product (which was saved successfully) appears in the category, Layered Navigation works as expected, so it has to be something to do with the attribute values and not the attribute itself.

* EDIT 2 *

Using Firebear Import/Export, I mapped the problematic attributes and exported them against the SKU. It only returned the SKU column, suggesting that the attribute values just don't exist at all. Either that, or there's no association between product and option.

Answer 1

Ok, I didn't solve the problem how I wanted, but I just ended up stripping out the problematic attributes and re-importing them using traditional methods.