PTZ cameras hung in the self test

dear sir , I have problem with 3 of 11 PTZ cameras I have in my cctv system ..

when I switch off the sysem and them swich on all PTZ cameras star to do self test 3 cameras when reach the tilt check it stop moving and hung up , some times I go an bush the camera which hunge up it start move some times not ... when I try to check the camera in my control room it work nice and when I fix it in the site it do the same fault ... note I have 11 PTZ cameras same model ...

thank to all....

I'd guess a power issue at 3 locations. What happens when you swap a camera from a position that works into a position where the camera was giving problems? How about the problem camera into a different location where the camera was working? Are the three problem locations getting power from the same source? Different cheaper cables or longer cable runs at those locations causing power drop? What happens if you power up the cameras one after another, not all at the same time like you are now?

thanks Mr. kawboy,

I will try your steps .. may be power problem ... becouse it is happen in the same place with different cameras!!!!! same times I miss simple logic >>> thank you