I am a homeowner. Hydronmodule Colony Series Plus WWD72. One unit for hyronic radiant floor in basement and garage coil. The other unit is for forced air on main floor of home. When very cold out and all being used a lot, unit 1 (forced air on main floor) goes into lockout. Last year this happened and installer troubleshoot with me there and figured low water flow because of blockage. I flushed through system with "iron out" and replaced a ball valve that was caked/restricted. Worked fine with ball valve for source to unit 2 (radiant floor and garage coil) partially closed. Has worked until the last cold spell here (-20) and then I see unit 1 going into lockout again. We also see a noticeable pressure drop at shower/faucet when both units running. Ideas I have: source in lines/valves/flow restrictor restricted, well supply line restricted, pressure tank problem, well pump getting weak (13 years old). Ideas anyone? Thanks! Here is a diagram of the system.