I have not had any issues with my Panasonic DP-UB420. It larger than the Sony x700 and runs  cooler. I have never seen it freeze. Never had to unplug it.
I didn't get the 820 as the 420 does everything I need. The DP-UB420 has a ton of features:
	
	
		
			
				
			
			
				
				4K Ultra HD Blu-ray Player with Wi-Fi
				
					
						
							
						
					
					www.crutchfield.com
				
 
			 
		 
	 
I wish I got mine for $149 instead of $250...