Do you know if the unit was purged with nitrogen after the repairs were completed? It sounds like some scale developed in the tubing after the soldering and a piece broke off and is blocking the tubing. It might come out if you have the unit evacuated, purged and then re-charged, but it is a long shot.
Lew Farber...RVIA Certified Master Tech...ABYC Certified Master Marine Electrician
SOLAR TECH ENERGY SYSTEMS, INC.
AM SOLAR ...MAGNUM…VICTRON ENERGY...LITHIUM & LIFELINE BATTERIES…MARINE REFRIGERATION