I like the LG 4K monitor very much but I've had a number of problems w/ it when restarting my 2017 iMac. Recently I couldn't get it to come to life after a power failure in the house and sent it in to LG for repair. About $160 later it came back in working condition. The factory put a cryptic note about resetting something in the monitor. A week later another power failure (we have them now and again in these parts) knocked it out. After quite a bit of experimentation I found that Apple's "D" restart option seemed to allow this monitor to reset itself after a try or three. I also had to play around with plugging and unplugging the LG's USB-C plug during start-up. Anyway, long story short it is currently working.