Problems with Brand New NexStar 4

Hi,

I have a brand new Nexstar 4 that has a strange problem. After I have
aligned the telescope I choose an object to view and slew over to it.
Lets say Mars. I wait for the telescope to stop slewing and I can see
Mars just fine. Now the problem starts. After about 30 seconds the
telescope move up in alitude and Mars disappears out the bottom of the
FOV. I use the direction buttons and move MARS back into FOV. After a
short time it happens again. This can go on all night. I have done the
following: Changed batteries, use power adapter, set tracking to
alt-azm, change slew rates, change back-lash settings. Nothing gets
rid of the problem. This also happens with any object I pick, moon,
planet, star. Celestron tech-support has no good solution except to
send the telescope back to them for inspection. I has hoping that
somebody else has seen this and knows what is wrong otherwise I be
sending the telescope back. This was supposed to be a birthday present
for my son's eight birthday. His first telescope. When this happens
you can actually hear it. It sounds like a slow paced clicking noise.
Other than this problem the telescope works and tracks just fine.

Thanks for any help sent my way.
---jerry