External display handshake timeout

Hello,

when I connect my external display (Samsung SyncMaster 2693HM) with the Elgato Thunderbolt Dock via HDMI, the "handshake" often doesn't work:

The internal screen becomes the secondary display and the external display receives a signal (Blue power LED). But before the external display can show anything, the MacBook changes back to single-display mode. After that the process starts again and loops. If I am lucky, after some loops the external monitor works, but it takes ages.

I also contacted the Elgato support, but it seems they cannot do anything.

Is it possible to increase the timelimit of the "handshake"?

I am using a MacBook Pro Retina Late 2013 with OSX Mavericks 10.9.3