It is possible to have multiple Form Mappings configured to a single element, however, this is bad practice as the value that displays in the form on the app is unpredictable.
Inspect an Element's Mapping tab
1. An asterix (*) will appear on the left-hand side of the Mapping tab in an Edit Properties Window where there is a Form Mapping to that particular element.
If you see more than one asterix, then there is more than one Form Mapping configured to the element.
2. Remove one of the Mapping Details by selecting the radio button Don't include this element.
Now only one asterix can be seen, meaning there is only one Form Mapping configured to this Element.
3. Save your changes.