Without your qvw or at least a sample and you don't describe the object in which the problem is occurring, so I can only guess - but here goes. I suspect that you have more than one possible value of Field1in the object at the point where you are trying to evaluate the expression.
If you want to detect if something is selected in Field1, you can use GetSelectedCount(Field1) or GetPossibleCount(Field1).
If you want to detect the one and only value selected, try If(Only(Field1) = 'Value',..)
If you want to detect if Field1 is one of several possible values, then use something like this
If(WildMatch('.' & Concat(Field1, '.') & '.', '*.Value.*'), ....)
Hope that helps