I have a few Apple TV 4K on the network. Wireless not a hassle. Wired well they are problem children.
 
The wired clients, every few seconds, give me Port STP changes/Port status changes as in designated→disabled/old: 1Gfdx, new: down/ old: down, new: 1Gfdx
 
And these are sleeping devices.
 
Which also give a high proportion of CRC align errors, only on received. When the Apple TV 4K's are actively streaming, Airplaying the CRC errors disappear. 
 
So the theory is on a wired client in order for the AppleTV to act as a HomeKit hub Apple has designed a special WOL packet that messes with Meraki Switches. And the reason the wireless clients are a bother is a) no WOL for you and b) I think Apple uses the sign into iCloud to provide that functionality.
 
Of course I could be way off here but has any one else seen the flapping Apple TV 4K?
 
I reached out to Meraki support but nothing more that, new cable, new port and new switch, all of which have not resolved.