PSA: Apple had a run of bad graphics cards in their 2015 MacBooks. I've had three bad, brand-new-out-of-the-box laptops since January. I bought the older model hoping to avoid any potentially unknown issues with the 2016/17 models. But it seems that would've been a safer bet than a 2015.
I'm sitting at the store now waiting to see how they're going to solve bad laptop #3 for me.
If you have a 2015 MacBook and have screen flickering or display issues, document with video and get it to the show ASAP. The issues will worsen over time until your screen goes out.
Update: the customer service at the Apple store in Leawood, KS has been outstanding. These guys really care, and are helping me out.