Setup vs. Portable - problems with MACs

Hi. I have used WinSCP for years in portable mode. Today I have problems to connect with the portable version: "Couldn't agree a client-to-server MAC [...]". PuTTY works perfect. So I tried WinSCP setup and it works perfect, too. All settings were cleared. Any ideas?

Versions tried: 5.19.6 (portable and setup) 5.20.1 (portable and setup)

Greetings

Please attach session logs from both.