Link with %20 is OK.
Try it yourself in any browser:
https://lubimyczytac.pl/szukaj/ksiaz...a%20Leibowitza
I'm stumped.
I checked on two computers, a total of four versions of calibre – works every time.
It works even if I create an empty book, only with the title.
Maybe some anti-virus or firewall? But this is doubtful since other sources of metadata are working ...
I will think about it, although I have no point of reference and I can't repeat the problem at home. If any new symptom appears, let me know.
EDIT: I just installed calibre on a third computer. I added a plugin and it works.
So I could write: SOA#1*3.