You are not meant to run the code above in the Event Tick, otherwise it will continuously try to zero player’s offset respect to the Head Target Position, which makes for a very uncomfortable VR experience. You should call it only once, at the beginning of the experience, to place the player where it should be.
During the experience (Event Tick), you can check if the player has moved significantly away from Head Target Position and give them some indication (for example darken their vision) that they need to return toward that point as suggested by @mordentral above.