Had a similar incident recently. First time I’d flown QF economy for ages and I remembered why! Fortunately only a SYD-AKL. Both pax on the same ticket. Had checked in online and allocated A & B seats.  Had an error message at the kiosk and flagged down a staff member who took over and said “oh it’s just got a note that I need to tell you your seats changed because someone just paid for the ones you had selected”. We were reallocated B seats well apart from each other. 
Care factor was slim and just got a shrugged shoulder.
	
		
			
		
		
	
				
			Care factor was slim and just got a shrugged shoulder.
				
						
 
 
 
 
 
 
 
 
 
 
 
 
 