For the average person, this is not a concern at all. False Memory Syndrome can possibly occur only when a poorly trained therapist (usually a Psychotherapist) uses hypnosis with an emotionally unstable client to supposedly "uncover" repressed memories. The unskilled therapist asks leading questions in an effort to "uncover" theorized child abuse, or find "proof" of the therapist's own conspiratorial notions of satanic rituals, or UFO abductions. This can confuse the unstable client and is serving the therapist's agenda, not the client's. The average person would quickly begin to suspect something was inappropriate and simply either terminate the hypnosis session by opening their eyes or not return to therapy afterward.
Generally speaking, hypnosis should not be used with an emotionally or mentally unstable person anyway. A good Hypnotherapist is trained to refer such a person to another Mental Health Professional. Make sure your Hypnotherapist is currently certified by a well-established hypnotherapy certification association (and therefore accountable) like the American Council of Hypnotist Examiners, and has had at least 200 to 300 hours of specific training in hypnosis. Bear in mind that having an advanced degree in psychology or medicine may give a practitioner the right to claim that they can do hypnosis as part of the services they offer, but that is no guarantee that they have had specialized training or adequate experience in the holistic art of Hypnotherapy.
In fact, the most well documented case of False Memory Syndrome occurred with a very manipulative American Psychiatrist who also put their emotionally unstable patient on powerful psychiatric medication and used coercive techniques in "psychotherapy" to forcefully suggest the patient had experienced something in childhood they had not. (It was later revealed that the Psychiatrist needed support for their pet theory of wide-spread satanic rituals taking place in America so they could write a book about it.)
Throughout the ordeal, which lasted over the course of several years, the patient periodically expressed their disbelief, only to be overridden by the MD (or "Medical Deity") and prescribed more brain-numbing medications. It took a great deal of time, constant duress, and the use of powerful drugs for the Psychiatrist to establish this false memory syndrome in their patient, which was very painful for the patient, but ultimately not permanent. Although this makes a great tabloid news story, it could never happen in short-term, goal oriented Hypnotherapy, even with a poorly trained Hypnotherapist. As far as memory serves us, no two people have the exact same memory of the exact same event that actually did happen anyway!