Before replacing the oxygen valve assembly:

You must install the oxygen regulator assembly before reinstalling the oxygen valve assembly

When reinstalling the oxygen valve, make sure the oxygen regulator and oxygen flow sensor are fully installed to the oxygen valve assembly

Always inspect the O-rings between interconnecting parts, and replace them if they are visibly damaged or rough to the touch.

Always use new O-rings supplied with replacement parts

Lightly lubricate O-rings with Krytox GPL226 lubricant when installing, and relubricate at every reinstallation