Flag images are not uniform.

[epeeme]

Replace with a standard (free) png flag pack preferable using ISO 3166-1 alpha-3 naming or look at a way of using ISO 3166-1 alpha-2 as an alternative.

The solution could be this - https://kfpun.com/flag-css/

[epeeme]

On first test some flag sizes appeared differently so will need to add styling to make them all the same. Also my existing ISO 3166-1 alpha-3 naming is wrong for some countries, so flags were not displayed. These will all need to be individually checked.

https://en.wikipedia.org/wiki/List_of_ISO_3166_country_codes