Re: It Happened Before! To Seles!
These are both high profile matches with big stars competing and a large audience. If it can happen in circumstances such as these with the most experienced of umpires at the helm you can bet your bottom dollar that it has happen many more times in much less high profile matches. I suspect things like this probably happen over on the ITF circuit 20+ times a year, perhaps substantially more than that. Probably quite often the mistake would go unnoticed by all in attendence including the players.