When reestablishing the display connection on wakeup it's possible the machine doesn't think there's enough bandwidth for 4K, temporarily. This theory is also supported by the fact that lower bandwidth modes don't exhibit the bug.
Next I would suggest trying to replace the cable with one that's higher quality.
When reestablishing the display connection on wakeup it's possible the machine doesn't think there's enough bandwidth for 4K, temporarily. This theory is also supported by the fact that lower bandwidth modes don't exhibit the bug.
Next I would suggest trying to replace the cable with one that's higher quality.