Missingt - Cannot read new strings added to the language file you are editing. Unfortunately Missingt does not let you add a new string so you do need to edit it outside Missingt but when you read the file again for translation, the string added just does not get read, like if it's not existing?
Missingt zaps all the comments in the file so figuring out where you are in a translation is not easy.
Wish the old Translation Manager would work in 2.5.
Unfortunately, I cannot help, not a programmer but I would definitely buy a good extension to help in translation efforts.