First of all, you should regularely check your translation for tag errors (F8) min. once an hour.
Besides this, it is generally recommended to run the command File > Save Target As ... during translation as often as possible, min. twice per hour. This option generates a clean target file from the current state of the translation and helps you to control from the very beginning, that the hitherto existing translation is technically correct and may be cleaned up without further ado.
How to ensure proper target file generation when working with client's SDL Trados Studio packages:
First of all, you should regularely check your translation for tag errors (F8) min. once an hour.
Besides this, it is generally recommended to run the command File > Save Target As ... during translation as often as possible, min. twice per hour. This option generates a clean target file from the current state of the translation and helps you to control from the very beginning, that the hitherto existing translation is technically correct and may be cleaned up without further ado.
If you open an SDL project package from a client, wherein the Save target option fails already from the very beginning, you should not proceed with this project package but work directly with the client’s source files and TMs by adding them to your own SDL Trados Studio project.
The following procedures are recommended:
1) In case you have not yet started with the translation but have already received error messages in connection with the client’s package:
Open the original source file (e.g. *.docx) in SDL Trados Studio and save it to a location of your preference. This creates a new SDL Trados Studio project with a folder structure at the specified location. Assign the client TM from the project folder that was created when opening the client's package to this new project (in the Projects pane, select your new project by double-clicking it and choose Project >Project settings >All language pairs >Translation Memories >Add).
Proceed with translation in this new project as usual. Remember, though, to regularely press F8 and save your translation as target file, to check for errors on the run and to determine more precisely at which point the target data generation fails.
When having completed the translation without issues, you should be able to generate the deliverables, i.e. final target file (e.g. *.docx) and the translated bilingual SDLXLIFF file without any further problems.
2) In case you have already translated files in the client’s package, but cannot save them as target files, although all tag errors have already been eliminated, proceed as follows:
Create a new empty TM and import your completed SDLXLIFF file into this TM.
Pretranslate the client's original source file (e.g. *.docx) with this TM. All fuzzy or empty segements in the file eventually represent sources of errors. Complete the translation of this new file as usual and output it as final SDLXLIFF and clean target file (e.g. *.docx).