I'm wondering why each machine is sending the same messages twice but with different Len values and the same Seq numbers. It just looks funny to me. I have no idea if that would lead to anything not working.
Oh look at the fifth line in the TCP dump. The Ack number is 3107781240 but I think that is supposed to match the Seq number of the previous packet from the other direction. ie it should match 3107781192. Now when unixmgr got the wrong Ack it maybe waits until it gets a good one or it might resend it's last message. Then again maybe I'm not seeing all of the traffic or I could be mistaken about how it works (it's been a while since I've dealt with this stuff).
Also are you able to SSH from a command line and is it just from Perl that it doesn't work? Is it just one command that fails when called via SSH in Perl?