It doesn't work.
This happens all of the time and is usually because the builder put in the cheapest grade switch or outlet in your home like I said before.
These are called utility or home owner grade receptacles and switches.
When you replace them use spec or commercial grade replacements.
They are more costly but by far a better choice.
Here are some things to consider.
You have to jiggle the plug to get the lamp or whatever to work.
Check the receptacle with another device.
If it is just that one device them it is what I call an intermittent open circuit with your appliance AKA device.
Why should you be concerned.
You have a poor connection and regardless of what the problem is it needs to be fixed.
These problem children can cause a fire due to sparks or the poor connection heating up.
This is also why this stuff is put in an electrical box.
Remember those weak legs we talked about.
Worth