Why does the camera keep losing track?

If you are using the GPU reconstruction, then the following tricks can help:

• Avoid flat walls and empty regions during the scan. Make sure you include part of the floor or some furniture to keep the tracking precise and stable.
• When scanning small objects, using a turntable and keeping the camera fixed is usually better.
• Also, if the object to be scanned is small or has few geometry, you can help the tracking by adding other objects around it. You will be able to crop the object of interest afterwards.

Also, make sure you move slowly and smoothly during the scan. Big gaps between frames can lead to tracking failure. If your FPS is too low (e.g. < 10 FPS), then you should probably consider getting a better graphics card.