As the wireless carrier that has done the greatest amount of work to stamp its mark onto the newly launched Nexus 6, AT&T is said to have sent the largest amount of the handsets back to Motorola, more than any other cell service provider.

Google carefully selects its Nexus partners, looking for companies that can execute flawlessly on the hardware designs required to optimize the experience of the latest version of the Android OS.

While many consumers purchase Nexus devices to experience Android in the state its makers intended it to be enjoyed, AT&T has sought to make its version of the Nexus 6 stand out from the variants at other carriers. The U.S.'s second-largest wireless carrier also added in a few features to maximize the return on its investment of the phone, which, like other handsets, are subsidized through contracts.

Consumers who purchased the Nexus 6 from AT&T have been experiencing screen issues, which render the displays black and make the handset virtually unusable. The bug is also said to create connectivity issues

By some reports, the problem stems from accidental use of old software. The software issue was said to have only affected the first batch of Nexus phones that were configured to AT&T's specifications.

For consumers who have been experiencing the blackout and connectivity bugs on AT&T's version of the Nexus 6, the best course of action is to get into contact with AT&T or Motorola. Both companies have already been replacing phones that have been plagued by the bugs.

Even if the problem is entirely due to old software and is remedied in short order, AT&T's revisions to the Nexus 6 have already irked many consumers. Though AT&T's version of the Nexus leaves the Android Lollipop ROM intact, the company has sewn in a locked SIM that ensures the wireless carrier's branding survives any attempts to flash, or re-install, the mobile OS.

The locked SIM ensures AT&T's logo will always appear on the Nexus 6 boot screen and the restrictive feature will also moderate tethering. Though not a new concept, users will have to pay AT&T to use the device's data-tethering capabilities. Tethering is connecting one device to another and sharing the Internet connection. Connections can be made over Wi-Fi, Bluetooth or by cable through a USB port, making the Internet-connected mobile device act as a portable wireless access point.

Along with stamping its logo onto the boot screen, AT&T has also thrown its own ringtones into the mix. However, the AT&T ringtones only add to those included by Motorola.