Forcing the card out again can cause internal damage to a micro switch at the back of the unit, and may also remove material from the card dot features.
If not jammed, the machines will no longer read any credit or debit card.
The machines are still accepting payment by cash, Snapper card, smartphone apps PayMyPark and Phone2Park, and text parking.
In addition to the existing payment methods, motorists can pay by calling council on 04 499 4444 and passing on their credit or debit card number and details in the strictest confidence while the issue is being resolved.
Replacing and upgrading the card readers in the city's 512 pay-and-display machines will be brought forward and take several weeks. Until the work is completed, temporary stickers on the machines will advise motorists to avoid using credit and debit cards and use one of the alternative payment methods.
The new readers will also incorporate paywave technology.
Normal enforcement of parking will continue in the CBD given that motorists have several payment methods available to them.
If motorists have received a ticket since the beginning of May 2018 after being unable to use a machine then they are urged to follow the appeals process that is outlined on the parking ticket.
The council will treat the appeals on a case-by-case basis – using its knowledge of which machines are operating and which have malfunctioned.