Can writing sandwich thesis in computer science be harmful to your career?
Regarding your career, don't worry at all. In computer science, it is mainly your publications, conferences, and your code in public repositories what's gonna be valued in real life. No one is ever gonna read your thesis, apart from (if you are lucky) the members of the committee evaluating it.

That being said...


  In the next months I will defend my thesis and I wonder if it is
  really worth it to write a traditional thesis.


The question here is: do you have a thesis in the research sense of the word (a statement about the world that you believe to be true and you have tried to prove during your PhD years)? From your description, it doesn't look like that's the case.

This would be my personal advice:


Case A: You already have a few good publications that answer some questions of a common broader topic. In my experience, it is worth to compile them, cleaning them out, and adding an introduction and some conclusions to help the reader prove you know what you are talking about, and that you are able to manage the big picture. It helps you clarify your thoughts and your research. That proves that you have a thesis, you are responsible for it, and you are able to defend your own research. You might actually learn a lot doing this.
Case B: You have been publishing here and there, about different topics, some of which don't actually have much to do with each other, and you don't really have a "thesis" per se. Then, honestly, don't bother. Just present your collection of publications and get your PhD. You cannot build and improvise a decent thesis in a few months if you don't have one already.
Case C: You don't have good publications and you don't have a thesis. Get your PhD and run away as fast as you can. Try not to recommend that University to anyone in the future.