Follow up:
After another quick check of things (adjustments, elec connections and voltage), along with finding 2 elec brake distributors to chat with, I am going with the magnets are just worn out. The wear hole indicators are either gone or barely visible. This trailer rolls 10k to 12k miles per year at 12k to 13k pounds, so I guess it is no surprise.
IMO, I highly doubt the brake assemblies are meant or expected to last that many miles. Realistically, unless you are a full timer, most TTs or 5ers probably do not see 30k miles in their life time.