Wireless standalone cameras can only record by PIR/motion. Where the camera is mounted can have an impact on how effective movement is picked up and recorded. 

Reasons:

1. Wireless cameras can record from 10 seconds up to 1 minute per recording. If the motion is continuous for more than a minute and continues across the camera (left to right, top to bottom), then it will stop recording at one minute and continue to record in another clip for the duration of the movement.
2. If the movement stops after a minute, the camera will stop recording. This means an intruder could still be standing on the same spot with subtle movements long enough to thwart the PIR/motion sensors. There is no fix other than that to utilize a security system camera instead to record continuously. 
3. Mounting any camera with thermal and motion sensors in the wrong location and angle can prevent recordings of certain movement. If the movement is isolated and small, the camera sensors may not be able to identify the changes between frames because the differences are subtle.