display – Cursor Lag / Stutter & Media Blacked Out

Wondering if anyone has a solution to the HDCP issues with external monitors. I’m fairly desperate for a solution.

I have a 2019 MBP 16, and I’m having cursor lag/stuttering, and media is blacked out on my new LG 4K monitor. Seems to be very, very common and yet I haven’t found a solution anywhere.

Things I’ve tried:

  • Reset smc and pram.
  • All different cables (currently using usb-c to DP).
  • All different resolutions and refresh rates.
  • The “detect displays” trick.
  • Safe mode (no problem in safe mode).
  • Toggling the auto graphics switching.
  • Disconnecting all other usb peripherals, and tried every port.
  • Resetting everything on the monitor.
  • Downloaded LG’s OnScreen Control, and Screen Manager; neither has any firmware update available or solution

Weird things:

  • Worked fine for about 2 hours after first hook up.
  • Works fine for about 1 minute after turning the monitor off and on.
  • Older monitors work great.

I’m working on a graduation project from a programming boot camp, so reinstalling OS or upgrading to Big Sur is a little too risky right now, plus I’ve read it actually gets worse with Big Sur.

I spend 12hrs a day working on this laptop, so if anyone has any input, I would be very grateful. It sounds like a common problem, and I find it hard to believe people are living with the mouse lag day to day.

Thank you!