Last week I was installing the pektsekye Calender, which allows you to add a date range to a product, instead of one day, which can be handy if your product has a return logistic.
For translation I copied the en_US.csv and translated it to Dutch, my native language.
Saved the file and draged it back into the app/code/vendor/module/i18n folder as nl_NL.csv
But no go. Even the product page did not want lo load any more . . .
After some searching I discovered that my text editor changed the read/write permissions
The permissions for "Everybody" where changed from "Read" to "Read/Write".
After I changed this back to "Read" only, all works perfectly.
I checked It again, but indeed, if saving a csv file with Text editor on a Mac the permissions are changed and the translation will not work.
If saved for example with TextWrangler everything is still in place like it should be.
Just thought I share this, may be to some use to somebody some day :-)
Any further comment are welcome off course!