problems with some translations

Hello!
I love the plugin, using it for a couple of sites, thank you! What I struggle, are translations (to _et (estonian). Every time after update some are missing for the invoice and strangely if I edit po file, they are still not appearing although in poedit looks everything relevant as translated corrected. Now
Invoice #:
Invoice Date:
Order Date:
Payment Method:
still in English although I edited po and mo files accordingly. I have also fixed some translation mistakes for the language and could send the better version to you, so in future updates we don’t get back to faulty translations.