Alexandra Nováková 

Is this for most projects or certain projects?

How long are your segments?
Is your project and project resources saved locally or placed on cloud/syncing solutions like OneDrive?
I am asking because I am factoring if performance is being compromised? Given it specific to when you are trying to confirm a segment and move to the next.

What I also want to address is when you say 

Alexandra Nováková said:

stops working and the document usually cannot be opened in Word anymore

Please explain the lodgic around this. You are in Studio Editor view. You are confirming segments. It stops working. 
How are you then getting the document in a state where it can be opened in Word?
Are you generating target documents throughout your translation process?

Also you mention:

Alexandra Nováková said:

he only way how to save my work is then to copy it from Trados to Word, which is pretty time-consuming,

Granted, you feel your project is "corrupt" and you feel the need to keep progress. Have you tried creating a second project but then apply pre-translate so that you are saving effort from copy/past among other things? Some basic instructions are here

Apart from understanding scale of issue + performance, a few ideas come to mind we can try reset shortcuts by following these instructions 

Looking forward to your reply

Lyds

The problem occurs with absolutely all longer project. Segments are usually of up to 3 lines. Sometimes, but no often, I merge two neighbouring segments when illogically split by the software after, for instance, a colon (:).

Projects are saved exclusively locally.

As regards the impossibility of opening the document in the original format – Word. When the error occurs in Trados, I save the document both in the original format (Word) and in Trados format. It is then impossible to open the one in Word, unlike in cases when everything works normally.

I have never tried the possibility you suggest, i.e. to apply “pre-translate”. Unfortunately, I have not been aware of such option. Thanks a lot, I’ll check that.

Thus, I’ll try both of your suggestions with my IT friend’s guidance and see it works. So far, I am very grateful for your help. May I kindly ask you to contact you again, if we cannot resolve this following your suggestions?
Thanks a lot. I wish you a nice day.

Novakova

Alexandra Nováková  absolutely please do keep in contact. 

Alexandra Nováková  absolutely please do keep in contact.