Modules menu in admin show HEADING_TITLE page when changing language

Payment, Shipping and Order Total can show correctly when selected under Modules menu in admin. However, when I change the language after selection, only HEADING_TITLE page will show as attached file. If I continue to change the language, same HEADING_TITLE page is showed.

If I select Payment, Shipping and Order Total under Modules menu again in that language, they can show correctly.

I tried to remove all payment modules and shipping modules but the problem is still the same.

Other menu have no problem when changing language.

No error log in Cache folder.

My zen cart version is 1.3.9f, PHP 5.3.1 and MySQL 5.1.42.

Could anyone suggest me what should I do? Thank you.

https://www.zen-cart.com/tutorials/index.php?article=95

DrByte:

https://www.zen-cart.com/tutorials/index.php?article=95
Thank you for your quick reply. After comparing and checking again and again in language files, I still cannot figure out what is wrong. It is because all can show titles and modules and funcation correctly if I selected them in individual language. However, when changing language under ...modules.php?set=payment or shipping or ordertotal, the problem happen again. Therefore, I guest something about language switching code in modules.php may related to this problem. As I am not good in coding, could you suggest where should I looking for?

Thank you.