This is more of a headscratcher than an actual problem.
I've created a public/private RSA key pair with Puttygen on Windows 10 and added the public key to an OpenSSH server on Ubuntu.
If I attempt to log in to the server using Putty, I'm asked to provide my passphrase. When I do so, I receive a "Wrong passphrase" message and am denied access. This happens both when I type my password manually and when I copy/paste it into the Putty window.
If I add the key to Pageant using the exact same passphrase, Pageant accepts it and I'm able to log in using Putty without issues.
I've got an identical issue with OpenSSH on RHEL.
Does anyone know why the exact same password is accepted by Pageant but rejected by the SSH server if provided manually? My best guesses are that it's something to do with key format and/or use of symbols in the passphrase, but I can't find any answers for this specific issue online.