If I were this couple's therapist, I would have the partner who has a paraphilic arousal pattern to take a step back and evaluate what their sexual interests are doing to the relationship. They have a partner who is consenting to the sexual activity, but with the continued dissatisfaction during sexual encounters it can put strain or even end the relationship. The consent from the one partner shows that they are trying to make the sexual experience enjoyable for their counterpart. It could be suggested that the paraphilic arousal pattern be broke, to bring a more positive mood into their sex. If there was no consent, then it becomes a legal matter, where the person performing the acts can face imprisonment or placement on the sex offender registry for the rest of their life. Consent and legality are absolutely key when participating in sex, but doesn't guarantee that your partner will get the same enjoyment out of it as you, which can put strain on the relationship.