Should be able to use wireshark if on windows.
Then just start capturing until you get a skip. Stop capturing, save the capture, and that’s it.
Those are kind of big-picture instructions — there are more details on how to select what interface to capture, etc, but I think you’ll find it isn’t too bad.
Once you’ve got a capture of the event, you can save just a few frames — the ones near the disconnect, and then it will be easy to see what’s going on.
Yell if this is too terse.
Firefly is running on a server install of FC4 here… I’ll start googling in the morning and see what I come up with.