I heard a great story a while back for a digitization project where historic content was being provided by many libraries around the world, including one in Russia.
The quality of the scanned books was excellent, except for a weird distortion every so often where part of the page would be shifted partway through as if someone had shifted half the page in Photoshop. This was only noticed in books over a certain size so people were checking to see if there was some kind of mechanical problem with the scanner (these were robots with automatic page turners so it was plausible that there could be something which was only an issue past a certain position), trying to figure out of there was some way that the software had some kind of memory leak or other issue which would explain the long and inconsistent intervals.
Eventually they were on a long-distance phone call to Moscow and not turning up anything when there was a loud rumble in the background. “What was that?” lead to the realization that the library's scan center was close to a subway tunnel. The vibration of a passing train was enough to cause a glitch but only if you happened to be scanning at the exact time it went by: the reason longer books were noticed was simply because having more pages meant that at any point in time a long book was more likely to be sitting in the scanner and the technicians running the scanner were apparently tuning out the trains as background noise. This was reportedly the first project they'd done with one of the scan robots which can process an entire book unattended so it was plausible that smaller past projects simply hadn't been scanning frequently enough to hit this problem or that some previous technician had noticed and immediately redone the page.
Not a native speaker so I didn't know what an air table was. But since I've worked in labs, I recognized it from the picture accompanying the Wikipedia article:
Indeed — they're not cheap but if you need that, it's worth the cost. In this case you could probably avoid it simply by having the robot rescan the page if it detected a vibration but the research labs I used to support had experiments where that would have jeopardized months worth of work.
I deal with this all the time at work. People are capable of tuning out frighteningly obvious things, if they happen with enough regularity for long enough.
The quality of the scanned books was excellent, except for a weird distortion every so often where part of the page would be shifted partway through as if someone had shifted half the page in Photoshop. This was only noticed in books over a certain size so people were checking to see if there was some kind of mechanical problem with the scanner (these were robots with automatic page turners so it was plausible that there could be something which was only an issue past a certain position), trying to figure out of there was some way that the software had some kind of memory leak or other issue which would explain the long and inconsistent intervals.
Eventually they were on a long-distance phone call to Moscow and not turning up anything when there was a loud rumble in the background. “What was that?” lead to the realization that the library's scan center was close to a subway tunnel. The vibration of a passing train was enough to cause a glitch but only if you happened to be scanning at the exact time it went by: the reason longer books were noticed was simply because having more pages meant that at any point in time a long book was more likely to be sitting in the scanner and the technicians running the scanner were apparently tuning out the trains as background noise. This was reportedly the first project they'd done with one of the scan robots which can process an entire book unattended so it was plausible that smaller past projects simply hadn't been scanning frequently enough to hit this problem or that some previous technician had noticed and immediately redone the page.