InDesign adds automatically a space within a number

Dear community,

Thank you very much for your enthusiasm to help. The discussion made it clear to think over the problem a while and to look for more experience. I could sort out the problem somehow, in that it needs to be split in two parts. The first part is misleading. It only looks like the issue is the recurring appearance of the unwanted space between two digits. As more recent experience showed, the issue is that the program does not keep your changes properly when several very similar files are open at the same time. Working with another "cluster" of open files, I changed a line in file 1, jumped to file 2 changing the same line, jumped to file 3 changing the same line, jumped back to file 1. Suprise, the line in file 1 had jumped back to the previous version.

Back to the unwanted space. It was the same situation, just affecting a space, which returned after deleting it in several other files at the same spot.

At any rate, I will avoid to have similar files simultaneously open and editing. Open, edit, save, and close a file every time is slow but save. 

P.S.: You might ask why this guy works with very similar open files. I am in the music business and need to edit orchestra parts from time to time. The parts are often just one page, with a one-page *.svg graphics, different for each part, and the recurring text on every part is impressum stuff in a frame.