I just installed gpg4win 2.3.4 on top of 2.3.3. Before running the installer I checked the signature of installation binary. There seem to be sequence problem in the installation process because before running the kill-agent script the installer tries to replace file libksba-8.dll which failed because it was in use by scdaemon. exe.
Shouldn't be the agent killed before the replacement of any file?

scdeamon is a subprocess of gpg-agent which is a separate process started when checking the signature of a file.