When decrypting a OpenPGP encrypted file with spaces in the name the "Decrypt/Verify" window shows the name correctly in the first line, but with escaped spaces for "name of the embedded file" further down:
The file had not been renamed, of course.
Subsequently you are asked under which of the namens - the embedded with "%20" or the original with " " you want to save the file.
The "%20" should not appear in the embedded file name.