It might be a poor connection between the PCB and the lens module. Could you please try as suggested in How to replace RunCam 2's lens module?
If it doesn't help, please try to fix the connection by:
attaching thin tape on the following area to make sure the lens module can connect stably with the PCB。
If the problem persists, please put tape to below part as well:
If it still does in vain, please show us clear pictures of your camera by all angles and your order invoice including the order date. Thanks.