Amazon originally planned to open its first Amazon Go store by the end of the month, but the king of e-commerce is pushing that date back to resolve some technological problems.

The store in Amazon's Seattle hometown will be the first to use Amazon’s cashier-free technology, which lets customers simply walk into the store, sign into the shop’s app, take what they need and walk out. The technology entirely eliminates the checkout process, but people familiar with the matter said Amazon’s current technology is encountering problems when there are more than 20 people in the store, the Wall Street Journal reports. The e-commerce behemoth is also encountering issues with not being able to track how much a product costs if it has been moved from its original position on the shelf.

The company is working with employees to beta test the store and perfect the technology, which works seamlessly when there are fewer than 20 people present making very slow, calculated moves. Until the kinks are worked out the store opening has been pushed with no mention of an alternative date, and Amazon has not commented on the delay.