There are some characters that are not supported in Windows (Windows illegal filename characters - can't find the github bug report) but I don’t see any of them in your URL. And the path should not be longer than 255 characters (File names too long - issue with NTFS filename compliance), including folders. But it is not the case either.
If the client blocks it, why do you get a bad server request (= the client is trying to upload)?
I was able to sync such a file (between date and hour I put a space):
It’s NC 30.