Virtual Scene Jumps Unexpectedly, but Boundary Does Not

I'm developing a virtual reality application (using the XR Interaction Toolkit in Unity) for use in a research study, and am having an unusual tracking issue. The application involves a 30-foot by 30-foot virtual room, and the user walks around this room during the study. Every several minutes, however, the virtual room suddenly “jumps” to a new location, such that the user is suddenly in a different part of the room or is outside the room entirely.

This is not coming from a boundary tracking issue. I know this because when the room jumps to a new location, the boundaries stay exactly where they originally were relative to the physical room where the study is being conducted. I also know that the headsets are not picking up on an old set of boundaries that was previously drawn in the same physical space, because idiosyncrasies of the boundaries we drew just a few minutes before—such as the shapes of the corners of the boundaries—are still exactly the same after the virtual room jumps to a new location. Instead, only the virtual room is jumping around, while the boundaries stay exactly as they were.

I've experienced the same issue on two separate Quest 2 headsets (the only two I have access to). This occurs not only when the user moves suddenly, but also on occasions when they are walking slowly around the room without abrupt motions, and suddenly sees the virtual room jump to a new spot.

Here are a few unusual features of how we are using the Quest 2, in case any of these may be relevant:

1. The physical room that the study takes place in is a large room, considerably larger than the 30-foot by 30-foot virtual room. Again, the boundaries are staying properly anchored on the physical room, so I don't know that the size of the room matters.
2. The person walking around the room with the headset does NOT hold the controllers as they do so. Instead, the controllers are held by a research assistant who is positioned outside of the boundaries, up to 30 feet from the research participant. We have disabled buttons on the controllers that could be causing the room to jump from one spot to another, but I don't know whether the physical distance of the headset from the controllers could be causing any of these issues.

Thanks very much for your help!