I actually find the most problems with Moan, even though their supposed to be good, their probably manufactured in some third work country now.
Good luck with your wording in the report, the least they can say if that isn’t the problem to tried, you certainly cannot see inside them, I have frequently founded objects become lodged in the cartridge, especially in bank owned properties which have sat vacant for a long while. Pieces of PEX, pieces of Copper, you name it, I’ve see it in the sinks-tubs-showers when first operated.
I have even disassembled numerous myself in the past at friend homes and at inspections, let the water rinse the fittings-components (after all the crap is out of the water, lubricate with non-petroleum based lube), good to go.
Have you noticed the pure black water loaded with mineral deposits when first running hot water which has sat stagnate for a year+; not pretty. I usually remove the aerators to allow full flow without restriction to get all the crap out of the supply lines, it helps tremendously to save mixing valves. Crap also gets lodges in the Ball or Gate Valves, I usually turn them on-off a couple time if pressure is still insufficient, but seldom touch Gate Valves unless their in a house built within the last couple years, never had one fail.