File sharing copy of large file over GigE hangs server

I have been trying to figure out what causes this hang. I have a Mac OS X server machine (Mac OS X 10.8.5) and have file sharing enabled. I also have a GigE network, and have recently replaced a bunch of cables, so I'm sure this is not a cabling problem.

If I try to copy a 50+ Gig file from the server to a client, and the client is *fast* enough, I reliably get a hang on the client.

Today, I tried logging in to the server and killing /usr/sbin/AppleFileServer and when I killed it, the "hang" ended.

While the hang is in progress, other network activity to and from the server continues without incident. The socket between port 548 (AFP) and the client has no buffered data during the hang.

This looks like bug in the AppleShare file server to me. Does anyone know anything about it?