We test every instrument function in every set before we ship it to ensure proper operation.  We strongly advise you check the instruments prior to final installation to ensure nothing has been damaged in shipping as it is much easier to trouble shoot them at that time.
If your "pre-check" finds no problems and you have an issue after installation you will need to determine what happened during installation to cause the problem. We will provide as much support as possible to help you track down the source of a problem but in the worst case scenario you may have to return the instruments to us so we can determine what happened and repair them.