SSL Handshake failure even both partners have correct certificates installed

Hi guys,

we want to create an oftp2 connection with one of our partners. The partner should send us files but everytime he does this we get the ssl handshake failure error. We both uploaded our certificates to the oftp application but still getting the error. We checked all settings and everything else. The curious thing is that when we send a file to the partner once we get the ssl error too but when we directly send a second file the first file is transmitted succesfully. How is this possible?

Kind regards
Bastian