I recently got a used Dell U2413 as a secondary monitor to my MBP (15" Mid 2012, non-retina, macOS Sierra). I'm currently an experiencing an issue where the external display would shut off, including its power led, 30mins to an hour after turning it on with the laptop. I would have to either unplug the monitor and wait a few minutes, or just wait until the monitor turns itself back on. I tried using the monitor with different sources (PC, android tv box) and all seem to be working fine. I also tried to boot to a Yosemite backup drive and it was working perfectly fine. Do you guys have an idea why? Thanks!