Final answer:
Using more than one washer between the cylinder and yoke when replacing an O2 tank can lead to a regulator malfunction.
Step-by-step explanation:
When replacing an O2 tank, using more than one washer between the cylinder and yoke can lead to a regulator malfunction. The washer is designed to create a seal between the tank and the yoke, allowing for proper oxygen flow. Using multiple washers can cause an uneven seal, leading to a malfunctioning regulator that may not deliver oxygen properly.