Whenever I boot the machine, or wake it from sleep, with an external monitor connected, the laptop screen flicker and dim/undim for at least a whole minute (while the external display remains black) before finally turning on. While this is going on the machine is also very slow, and responds poorly to keyboard/trackpad input. This does not happen if I do not have an external monitor connected.
- High Sierra 10.13.2 (17C88)
- Macbook Pro (15", 2017)
- External monitor is connected through an USB-C Digital AV Multiport Adapter (HDMI)
- The machine is connected to a power cable
What I've tried
I've tried resetting NVRAM and SMC to no avail.