Another "No Heat" Problem

I bought a 2004 Butler last fall. I've posted about it here before. I thought we had the heat problem fixed, but we didn't. We flushed the system, heat worked for a day.......new heater core.........worked for a couple more......new thermostat............bleed the system.......worked one day. I've got plenty of heat at the wand but none for the truck.
Turns out the problem "might be" deteriorating zip ties holding the coils together in the heat ex-changer getting into the system and clogging...

Another "No Heat" Problem