Each field in unit config can have formatter class set. When formatter is set to "kMultiLanguage" class, then during table scanning (when adding new language or pressing "Rebuild Multilingual Fields" in "System Tools" section) missing translatable fields are created, so we have 1 field for each language, like "l<LANGUAGE_ID>_<FIELD_NAME>".
* When "<FIELD_NAME>" is found in table, then it's parameters are used to create new translatable fields.
* When "<FIELD_NAME>" is not found, then we create translatable fields based on information from field declaration in unit config.
There is an error in regular expression, that checks, that we already have given field created in table resulting field being reported as existing, but it doesn't in fact. For example when you have field "DestName" in table and you have translatable field "Name", then "DestName" is matched instead of "Name" and none translatable fields are added.