Films in the mockumentary genre can be thoroughly satisfying entertainment experiences when done right, as seen in such examples as “Zelig” (1983), “This Is Spinal Tap” (1984) and “Fear of a Black Hat” (1993). But the key, as noted above, is in doing them right, something to which this latest such offering from writer-directors Nick Lieberman and Molly Gordon can’t lay claim. The problem here is that the picture is too hit or miss on too many fronts: When it’s on, it’s brilliant and genuinely hilarious (especially in the film’s final act); however, when it’s not, it tries too hard to be funny ...