Oxygen reacts spontaneously with sodium metal. (And various other things.) That causes current to go in and not come back out, but other things can cause that too.
When that happens, telling why can be complicated, but one way to tell if oxygen is the problem is to take away the oxygen and see if that helps.
How do you distinguish oxygen contamination from other problems, and what’s the mechanism by which oxygen causes problems?
Oxygen reacts spontaneously with sodium metal. (And various other things.) That causes current to go in and not come back out, but other things can cause that too.
When that happens, telling why can be complicated, but one way to tell if oxygen is the problem is to take away the oxygen and see if that helps.