Just my 2 cents...Ditch the two galvanized wands for SS...Also, you say the weep is daisy chained to each bay with what looks like 1/4" ID X 3/8" OD polytube?. Maybe this is creating the issue? Go back and look at how I designed my weep system and compare to how yours is plumbed. You see the difference? I have 5/8 ID hose supplying a 1/2" npt strainer and a 1/2" npt brass leg on the top. Then tee'd off the 1/2" supply to 1/4" fittings and needle valves. There is very little pressure difference between any of the 1/4" feeds to the needle valves because of the 1/2" supply. If I used 1/4" supply, pressure would drop to each tee with the end 90° fitting having the least pressure. Remember how I explained having a 1/2" supply in my house and how you got scalded in the shower when someone flushed the commode? There is a significant pressure drop on the cold supply since the water takes path of least resistance. Switching to 3/4" main supply to all the 1/2" branches minimizes pressure loss on the cold supply when the commode is flushed.
Same principal here. I think you'd see the same results if you plumbed yours the same way I did or at least supplied all your bay tees with something larger than 1/4" ID tubing. More like 1/2" or larger....Plus using larger supply hose or tubing helps slow water flow, minimizing water hammer. Also see how the weep-washer causes you problems? Here's a youtube video to support what I'm trying to explain...
https://www.youtube.com/watch?v=FPZ-F4XvQf0
I haven't had a freeze up since installing my new design AND installing all SS wands. I just looked at Kr, the 18" SS flex wand is only $1.42 more than galvanized? A no brainer!