If a data layer push unexpectedly overwrites an existing key-value pair instead of creating a new one, what is the most likely cause?

The most likely cause of a data layer push overwriting an existing key-value pair, instead of creating a new one, is that the new push uses the same key as the existing variable. The data layer, in its simplest form, is a JavaScript array of objects. When you push an object to the data layer with a key that already exists at the top level, the existing value for that key is replaced with the new value. For instance, if the data layer initially contains....