What is the best way to translate an updated user guide with Studio 2019?

Question

Hello everyone! 
 I work in a software company. Each year, our team must translate the updated user guide. I've aligned the previous versions of the user guide and pretranslated the 2020 version. I thought that Studio would pretranslated the guide and only let empty the segments concerning the new features i.e. the text to be translated. But the match rate isn't as high as I expected, because of the tags. 
 
 I have to confirm a lot of 93-99 % match segments manually. It's really time consuming. How could I avoid that? 
 Precision : the format of the source file has not been changed, since the previous version, so I don't understand why the tags aren't the same. 
 Thanks for your help!

Paul Filkin · Answer

Camille Bertrand-Sittler 
 If you translate these files every year do you keep the previous SDLXLIFF files from the translations created at the time? If you do then the best solution is to simply Perfect Match and don't align at all. You also have your TM from the previous translations, why don't you use that? There is nothing wrong with your approach, I just wondered. 
 On the alignment... a few questions: 
 
 what's the source file format? 
 have you got customised segmentation rules? 
 do the source and target have different tag structures? 
 did you use the same translation tool to handle this as the previous times? 
 can we see the source and target files?

Jerzy Czopik · Answer

No need to be sorry, I am trying to find out, what's happening and this is why I have so many questions. 
 So, it looks like within the previous translation, showing in your TM view, segments with missing tags have been confirmed. On the left, in source, you see tags surrounding the text, while on the target side these tags are missing. 
 There are multiple reasons for that. First: Studio does NOT show tags by default, just formatting. So when the translator seen the segments last time, there was no visible difference between the segment in source and target. Bold was bold and the font looked identical or at least similar. Second: Studio does NOT report missing formatting tags by default. So there were no errors in the process and no one noticed missing tags. 
 Solution: confirm all the segments again, create a new TM and import only the last translation there. Next time the process should work as expected. 
 Possible solution to make it faster: remove penalty for missing formatting and different formatting within your current project. Use pretranslate, this should insert all segments as 100%, even with different or missing tags. When done, revert these settings to default. Go to verification settings, tag verifier and change the settings to not ignore formatting tags and not to report spacing around tags. Run the verification for tags, repair any possible errors. When done, create a new TM, attach it to this project, remove the old one. Update the new TM with the new project and keep the project for future reference.

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What is the best way to translate an updated user guide with Studio 2019?