Showing "Error importing translation files" while adding a new language in drupal 8

I have properly installed all built-in language modules provided in drupal 8. Everything goes fine but whenever i add a new language in

Administration >> Configuration >> Regional and language >> languages

It always shows an error i.e.

An AJAX HTTP error occurred.
HTTP Result Code: 500
Debugging information follows.
Path: /[sitename]/batch?id=18&op=do_nojs&op=do
StatusText: Internal Server Error
ResponseText:

and shows this message at top "

Error importing translation files Please continue to the error page

".

I have tried to reinstall language modules by uninstalling it first and then install them again one by one, but still getting same error.

Any solutions will be helpful