Another issue is that deductions for Kiwisaver and other amounts are being taken at the wrong amount and/or not being paid to the correct recipient. If your employer doesn’t pay your Kiwisaver contribution to the IRD you may lose that contribution. If the right amount of tax isn’t paid you may find yourself with a large tax bill at the end of the year.
The length of time these issues have been allowed to carry on without being effectively addressed is completely unacceptable. You shouldn’t have to do so, but please check your pay carefully, and, if necessary, check with the third parties to whom deductions should have been paid.