When filming an investigation, usually in very low light settings, many of the same things can occur as with photography. That orb traveling across the screen is probably a bug or dust. The size of the orb, as with a photo, depends on how close the dust, pollen or bug is to the lens.
Low light video, even with infra-red (IR) lighting, is grainy. Often shadows in a room appear to move or take shape. Be certain you are not falling into the matrix trap. IR can frequently cause a shadow person to appear all by itself. A surge or fading of electrical or battery power can cause the IR to malfunction and create distortions.
Completely normal variations in lights and shadows appear in night vision video. The bright light shooting across the screen more often than not is the beam of a flashlight, headlights from a car coming through a window, or the glare of a light reflecting off a surface. As with all evidence review, it is really important to know where every team member or other people in the building are at all times.
A person can be standing out of camera view but reflect a shadow against a wall simply from an extraneous light source. Not long ago, a world famous celebrity died. A local news crew was shooting video for a TV piece in his former home. A spirit or shadow person was seen walking in a back room. It was all over the Internet. The shadow had a strong resemblance to the celebrity and looked so genuine. Turns out the shadow was cast by a TV crew member.