Although it’s been quite a while since you posted, I’m leaving a comment anyway. I checked the files, and there doesn’t seem to be any issue with the script itself. The problem seems to come from the insertion of translation keys like "LOC_CITY_NAME_BERLIN_GERMANY" or "LOC_CITY_NAME_SANAA_ARABIA" in the Spanish localization file, which don’t exist in other language XML files. To fix the translation issue, please either delete the entire GamePlayText_es_ES.xml file or manually remove the keys from it that aren’t present in the localization file for your current language.

I found a slightly simpler method.
In the 'YnAMP_Script.lua' file,

if bCanUseCivSpecificName and Locale.Lookup(sCityNameForCiv) ~= sCityNameForCiv and not IsNameUsedByCivilization(sCityNameForCiv, CivilizationTypeName) then

Change this condition to:

if bCanUseCivSpecificName and Locale.Lookup(sCityNameForCiv) ~= sCityNameForCiv and Locale.Lookup(name) ~= name and not IsNameUsedByCivilization(sCityNameForCiv, CivilizationTypeName) then

The condition 'and Locale.Lookup(name) ~= name' will help ensure that not only is 'sCityNameForCiv' translated in the current language, but the generic city name 'name' is also available in the currently active language.