Intermittent feature spec failures are the bane of testing experience.
They cause builds to fail at random (which really screws with you when you have continuous deployment based on master-branch merges). But more insidiously, they lead to bit-rot in your test suite - because once you get used to tests failing at random, you tend to overlook it when they do... which leads to bad code falling through the cracks at the worst times.
Patrick Bacon's article: These Intermittent Test Failures Will Not Stand, Man has a small selection of useful things you can do to address these failures and root them out for good.