Why iPhone 7 rear camera shakes and how to fix?
 

There are two reasons for the shaking problem of the iPhone 7 rear camera.
1. The rear camera is broken. Need to change the rear camera.
2. The rear camera circuit has malfunctioned.

How to fix the iPhone 7 rear camera shaking which was caused by malfunction of the rear camera circuit?
Step 1: Confirm the damaged rear camera circuit
Step 2: Locate the faulty component
Step 3: Clear fault
Step 4: Assemble the phone and test

Indeed correct failure isolation sequence. Shaking rear camera on IP7. slo-mo didn't shake but all other modes did. Magnet fix stopped shaking. Need to place in specific spot to stop shaking in video mode. Furthermore, magnet fix made picture blurrier suggesting it prevented focus adjustment.

Checked the logic board for shorts and saw none on pin 16 per following link above suggesting failure it the rear cam itself. Ordered a replacement and all fixed.