I use wordpress in spain lenguage, so in my folder /wp-content/languages/plugins/ I can see the following files:
I have download them in my computer. After that I have done changes in labels using POEDIT software (not the last version, but 1.8.13) and saved them.
After that I ave uploaded files using FTP in /wp-content/languages/plugins/
When I go to my web page, I can see changes. It is good. It runs well.
But after 1 hour, or 2 hours my web come back showing olds labels.
If I download buddypress-es_ES.po located in /wp-content/languages/plugins/ and open all changes I have done are deleted.
This happen after a few hours I have upload po and mo file.