You kind of want to slap everybody in Permission, and that's kind of the point. It's a wry twist on the rom-com dilemma of what keeps the lovers apart: They've been together too long.
Anna and Will (Rebecca Hall and Dan Stevens, two Brits playing New Yorkers) met as kids, dated since high school, never slept with anyone else and seem perfectly content. Yet when her brother Hale (played by David Joseph Craig, who's married to the film's writer/director, Brian Crano) and Hale's boyfriend Reece (played by Morgan Spector, who's married to Hall) suggest that they should sleep around before getting married, Anna and Will are surprisingly quick to agree. What follows is at first awkward (which I think is deliberate on Crano's part), then frustrating (which I fear isn't).
Ultimately, the film becomes a love letter to Hall, and that's what saves it. She's such a beautiful, prickly, intelligent, singular presence that you root for Anna, no matter how many questionable choices she and the film make.