My wife and I were walking in the park today and her phone just shut off with 50%+ left. When we started it up it reported 20% and dropped like a brick (2% a minute) until I let her borrow my small Anker 3200 mAh charger - which rocket charged the phone (in a few minutes) to 39% and stayed there even after unplugging for hours. Phone seems to be stuck on 39% now no matter how long its used or what charging is done to it. I plugged it into my Macbook and Coconut Battery shows health fine (97%) and no obvious problems. Any advice? Right now I am telling the wife to let it run to 0 (hard to do since the % hasn't changed for 4+ hours even though she is watching videos with full brightness(painful)) - then we'll charge it to 100% and see how it does. Please note this is a 6s+ not 6s. Has about 187 charge cycles and has behaved (up until now) flawlessly. Thanks for your time!