When using an application that records video (like Facebook Live, or BeLive TV) and Chrome I am experiencing monitor blackouts with my iMac that last for about 15-45 seconds, or sometimes more. The iMac screen, as well as my external monitor (connected via Thunderbolt to MiniDisplay cable), both go completely dark and the iMac is unresponsive to keyboard or mouse commands. I did not experience this with 10.13.3 on my iMac, and I don't experience it with 10.3.3 on my Macbook Pro that is connected to an LG 5k display via Thunderbolt. Anyone else seeing this? I found a few similar reports on Apple Discussions, and I did submit feedback to Apple. I believe that most of those reports mentioned an external monitor, and I saw some other reports suggesting that there may be an issue with 10.13.4 and displays.