Macbook Pro 2014 shuts down at random intervals
Please make sure you also check your Macbook for excessive dust inside! 

I have a Macbook pro which shutdown randomly (and gave the shutdown cause -128 error, and also the reference code PPT004 - the battery requires service). When I cleaned the build up dust it started functioning normally again!

I just removed the backplate and used a can of compressed air to clean it. Check https://www.ifixit.com/Device/Mac_Laptop to see how you can remove the backplate of your model.

PS: Try not to touch any parts inside, because of static discharge