To reproduce:

• I switched the game language from english to german.
• I picked up the Omious Banner item from a pillager during a raid. Its display name gets translated depending to the users selected language.
• I then saved and loaded the item to/from config.
• The loaded item will no longer match the previously saved item: Its display name will now be fixed and english.

Screenshot of the data of those two items (before and after saving/loading): https://prnt.sc/opq4yb

Possible plugin code for saving and loading items to/from config: https://pastebin.com/JgGxnLMH