Reports of late 2013, mid 2014 and even mid- 2015 MacBooks are getting bricked are popping up on social media including reddit and it seems like the issue is widespread.
Some Mac owners are reporting that they sent their devices for a repair and it seems the issue has been escalated to Apple higher ups.
It is unusual for these things to happen, no official update from Apple yet. Usually few micro-versions later these issues will be