We made it back to the facility today, and immediately tried playing the video from the camp. The picture is really bad, and there's no sound. It shows enough to be deeply unsettling, though.
In the video, you can see the researchers going in and out of the cavern, and setting up various experiments. When they aren't working, you can see them eating, or standing and talking. At 15:06, according to the time stamp, the researchers all stop what they're doing and turn toward the cavern. They stand still for a heartbeat, and then all run inside. The last researcher has disappeared before the time stamp reaches 15:07. The researchers do not come back out of the cavern, nor is any movement visible. We arrive hours later, and the video shows us entering the cavern to look for them.
It's possible that the researchers exited the cavern during one of the frequent periods when the picture was obscured by static. I don't think so, though. I don't think they came out.