what causes water pressure loss when sink water supply is closed to replace an undersink filter? Outside water inlet was also closed so that the hot water valve on the hot water tank could be replaced.Are these related cause and effect problems?
Possibly someone failed to open the valves fully and close them 1/4 turn back.
Another consideration is when a valve is closed and opened too fast the incoming rushing of water could dislodge sediment partially blocking aerators and piping