debug3: send packet: type 90  
   # This was the request to open a new channel (SSH_MSG_CHANNEL_OPEN)

debug3: receive packet: type 91
debug2: channel 1: open confirm rwindow 12288 rmax 512
   # That was the Ok response (SSH_MSG_CHANNEL_OPEN_CONFIRMATION)

debug3: receive packet: type 1
Received disconnect from 10.10.3.6 port 22:2: Disconnect Protocol error
   # And then, suddenly, an unexpected disconnect message saying "Protocol error"