In a sign of continuing troubles for Apple’s latest 27-inch iMac models, the company is now delaying new orders from its website by up to three weeks.

AppleInsider is reporting today that Apple is unable to fulfill new orders for the big screen desktops, while the 21.5-inch iMac models are currently shipping within 24 hours. As recently as a few days ago, the 27-inch iMac model had an improved shipping time of less than a week.

While Apple themselves may have no availability of the 27-inch iMac at the moment, authorized resellers are reporting that volume shipments have started making their way to their shelves, marking the first time they’ve been available at all since their introduction late last year.

The 27-inch iMac has been plagued with problems, with early adopters reporting screen flickering issues that forced Apple to notify resellers that their stock would be delayed by about two weeks. The Cupertino computer maker publicly apologized for the early problems, but never directly addressed that any hardware issues existed. However, Apple did release a software patch designed to fix the screen flickering problems on the 27-inch iMacs.

The latest big-screen iMacs have been a big hit with buyers, making them the best-selling desktop machines in the U.S. in the fiscal quarter they were introduced.