I generally try and replace these OEM cords. They tend to be a lower grade than the one Anker sells.
If the powerbank is bad. This is rare. Anker powercores and other products are designed to last for years. They even come with 18 month warranties. I would contact email@example.com @AnkerSupport and see what they can do for you. To speed up the support process, tell them what troubleshooting steps you have tried and the results you got. Also give them the product serial number, order number and where you purchased the powercore.
It may take a few days for them to respond. Support is closed but may have limit staff on duty and its a 4 day holiday weekend for many companies.