Problem with Magento attribute code and import/export

[GTLTD]

Hello. A couple of weeks ago after installing Magento 2.3.2, I created a couple of attributes with the attribute codes called 'Design and Size'. Magento let me use capital letters whilst creating the attribute, which I now know I shouldn't have used. I have changed the attribute_code fields in the eav_attribute table and flushed the caches and reindexed. The uppercase to lowercase change is reflected within the admin. However, when exporting products, the change is not showing in the spreadsheet, and attemping to import products indicates a problem with that column due to the attribute code. I have now created several hundred products using the attribute, so deleting it and creating a new one is not ideal. Does anyone know how to fix this?

[GTLTD]

I have since deleted the attributes with capital letters from within Magento and created new attributes with different titles. However when downloading newly-generated export CSVs the old attributes are still on there, and the new ones are not. Help resolving this would be really appreciated.

[verma_mallika]

I tried to create similar scenario but able generate issue.. When I changed attribute code from database it worked for me.
Can you please once try to clear cache and re index.
php bin/magento indexer:reindex
php bin/magento cache:flush
php bin/magento cache:clean

Then again try to export products.

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