UP2720Q or UP3221Q Resolution Locks at 3840 x 2160 at 30 Hz

The Mac Mini resolution is locked after waking up from sleep.

Affected Products:

Dell UltraSharp 27 4K PremierColor Monitor - UP2720Q
Dell UltraSharp 32 HDR PremierColor Monitor - UP3221Q

This issue is caused due to a Mac Mini resolution issue.

Multiple methods may be followed to resolve the resolution lock:

• Unplug and then plug back in the Thunderbolt (TBT) cable.
• Press the power button DC on/off.
• Unplug and then plug back in the AC power cable.
• Reboot the Mac Mini after shutdown.