AD9888 power related issue


Power relevant issue occurred on my customer's product on which AD9888 is used.

The detail is as follows.

The end-user powered up the product and keep on for more than 20,000 hours.

After that, they turned off the product for the periodic maintenance,

subsequently, they re-powered up the product but then it got not working.

According to customer factory's investigation, It seems that the power lines of AD9888 are shorted.

They think short point will become hot by adding the external voltage, so they added external voltage to the power line of AD9888 in order to find out the short point.

But halfway through the identification,  short point was removed suddenly and then the product got to work correctly.

Subsequently they turned off and on the product again and then the product got not working..

This issue occurred 4 pcs out of 8 pcs.

Could anyone teach us possible root causes and workaounds about this issue?