Syncing over the LAN at 1Gbps

[Isanderthul]

I have a backup node on my network with a blockchain that is fully synced,
I have my farmer that occasionally gets a corrupted database.
the farmer has port 8444 open and router port forwarding is enabled.

I copied the database from the backup node to the farmer, and restarted the farmer, then added the backup node to the list of farmer connections (currently 80 connections), so that the farmer could catch up the last few blocks.

The farmer shows the backup node as having a SB Height of 0, and MiB Down of 0.2. Eventually the backup node gets dropped from the list of connections.

(venv) root@gen8-full:/chia-blockchain# chia show -c 
FULL_NODE 192.168.0.101                           8444/8444  def99b45... Jan 20 12:45:05      0.0|0.2

I expected the farmer to pull from the backup node at 1Gbps, but MiB down is only 0.2,
Why is the farmer not pulling fast from the backup node?
What does SB height mean (is 0 bad?)?
Should I reduce the number of farmer peers? (setting the target_peer_count to a low value like 10)
Why is the backup node being removed from the connections?