There may be a loose neutral connection. That loose connection could be at another socket (receptacle) or in a switch box on the way (on a daisy chain) back to the breaker panel.
If the neutral has a loose connection, you can still get a shock if you touch both the hot wire or terminal and a grounded object.
When cleaning anything including baby diapers, it is better to sweep off or scrape off as much solid and semisolid material as you can first. (1) Less cleaning fluid or detergent needs to be used, (2) Less of a mushy mess which in turn means that bleaches or disinfectants will be more effective.