Pros do have aiming failures from time to time. More often than not when pros miss it's hard to tell why, but there are times when it's pretty obvious that the player lined up the shot wrong. What makes an aiming error even more obvious is when the player stays down on the shot and maintains a nice straight stroke throughout their delivery.
Here's an example of John Morro lining one up really bad during this year's World Pool Masters:
https://www.youtube.com/watch?v=JxxN6Ss-VPo#t=76m05s
They show it again in slow motion at the end of the rack:
https://www.youtube.com/watch?v=JxxN6Ss-VPo#t=79m20s
I bet there's a ton of them out there.
Here's an example of John Morro lining one up really bad during this year's World Pool Masters:
https://www.youtube.com/watch?v=JxxN6Ss-VPo#t=76m05s
They show it again in slow motion at the end of the rack:
https://www.youtube.com/watch?v=JxxN6Ss-VPo#t=79m20s
I bet there's a ton of them out there.