Bummer to hear you are having some issues with the Seraphim. I actually work for Curtis and deal mainly with customers using the Seraphim, so I would be glad to help you out with some suggestions for getting the most out of your brewer.
One of the first things I point people too is the temperature setting in the tank, but it seems you already have that area addressed by setting it to 206*. Even with the tank set there, I would highly recommend using the “pre-wet” setting to flush the head with a decent amount of water (15-17sec) to help keep everything hot. I know we try to address that issue by circulating water from the tank to the brew head throughout the brew cycle, but as we all know, any extra steps we can do to increase out temperature stability will always be beneficial.
Im assuming you are probably using a Kalita or v60 for brewing? Try to keep the brewing device as close as you can to the spray head to mitigate heat loss in the water from the spray head to the coffee bed. Another thing to take into consideration is the decrease of bed turbulence when using Seraphim vs. gooseneck kettle. Water is falling more gently on the coffee then when you use a gooseneck kettle, so bed turbulence drops a little bit when using the seraphim, which is why I really like to agitate the bed during the bloom. That being said, its always worth creating some recipes with one head calibrated for “no sprayhead” and see if that helps you bump up extraction percentage as well.
These are just a few quick suggestions I think could really help. If you have any other questions feel free to reach out to me via email: Angomez@wilburcurtis.com