Hello, we ran into the same issue and I discovered the problem. Pterodactyl's SFTP server does not support SSH in any way, so you'll need to add the --sftp-disable-hashcheck flag (I hope you don't have to compare hashes) to get this working. 
Hello, we ran into the same issue and I discovered the problem. Pterodactyl's SFTP server does not support SSH in any way, so you'll need to add the --sftp-disable-hashcheck flag (I hope you don't have to compare hashes) to get this working.