In case you’re learning about this issue for the first time, back in March 2017, Apple notified service technicians that there would be a severe constraint of top cases for the MacBook Pro models. For those unfamiliar, the top case is the aluminum enclosure of the MacBook Pro that houses the keyboard, trackpad, and speaker grilles.
However with the mid-2012 and early-2013 MacBook Pros, Apple actually glued the batteries for the laptop to the top case with a very strong adhesive, meaning that replacing the batteries was not as straightforward a task as it should have been. However now that it has been restocked, repairs should be back to normal.
However it should be noted that because supply levels for the batteries are back to normal, Apple will no longer be giving customers free repairs due to the delay. Instead Apple will charge customers its standard out-of-warranty fee which is $199, which is also waived if customers are under the AppleCare+ plan.