Hidden symbols out of nowhere in segments

Question

Hi, 
 
 We've noticed that in some segments, Trados seems to automatically add hidden symbols. So in Trados 2021, they look like extra spaces (no tags). When hidden symbols are not visible, the text looks completely normal. There don't seem to be extra spaces then. In the cleaned Word version, these so-called spaces look like 1 space and 2 squares, also only when hidden symbols are visible. When the hidden symbols is toggled off, the text looks normal. 
 Trados:

Word:

Any ideas what causes this? 
 The only thing I can think of, is that it has something to do with different Trados versions: the file was created with Trados 2021, but the Translator had an older Trados version. The switch to Trados 2021 was done recently. 
 
 Any help is appreciated, thanks

Jerzy Czopik · Answer

Oh, sorry. I must have missed something in your comment. 
 Well, what can have caused these signs are keyboard shortcuts inserting some characters outside from the visible charmap. These can come from the auto suggest function or from the MT. You see them as spaces in Studio, but these are not recognizable for Word and thus replaced by some strange symbols. In fact I cannot tell you where these exactly do come from, but the simplest solution is to delete these and forget about it. Only if that will be repeating itself more often there will be a need to investigate further. 
 Have you done any copy & paste here from Internet or other app?

Trados Studio > 1. Trados Studio

Hidden symbols out of nowhere in segments