Some interesting reading here, and a "senior moment"...
I don't recall there being any pre-Roamio issues with "Green" switches, which were on the market, and in use, before the Roamio came out, and then had major issues with them.
AFAIK & TTBOMK, TiVo addressed the issue, fully. I'm seeing a lot of people dredging this outdated issue into the here and now, like as if it was never fixed, over many threads, on differing subjects, and in relation to TiVo models that didn't have issues with them.
IEEE 802.3az - Is the standard for "energy efficient ethernet" AKA: "Green".
Wikipedia page devoted to it: http://en.wikipedia.org/wiki/Energy-Efficient_Ethernet
It's not much to take in, and is worth reading. I'd like to try and stop the game of "telephone" going on, which is propagating around, and may cause a lot of confusion and misinformation about the Roamio-only, already-addressed issue with Green switches.
Usually, a transfer that keeps stopping at the same point, is due to that recording having an A/V glitch at that point, and the transfer chokes on it.
Turn it around and look at the problem from another direction:
Could the receiving TiVo have a bad sector on the drive, something corrupted within the databases, or that TiVo possibly just "think it doesn't have enough space"?
I'd suggest using KMTTG to bulk-delete the Recently Deleted folder contents, on both TiVos, then reboot both. A KS52 (Emergency software re-install) is the safest way to initiate database repairs, and least likely to cause a GSOD boot-loop, like KS57/58 sometimes will do.
If that doesn't do the trick, then I'd suggest the next step be clearing program information & TDL, from the reboot menu. Again, I'd do this on both TiVos. Recordings will not be lost, Season Passes will repopulate, and thumb ratings will remain. I'd suggest also clearing the thumb ratings and suggestions, as they have hooks into the databases. If you are OK with clearing them, I'd make that something to do BEFORE a KS52 (for maximum results).
I have very little belief that transfers being cut at the same time has anything at all to do with the network, switches, or if they happen to be "green" switches.