Phosphates were banned in dishwasher detergents in 2011, so most of the name brand companies switched to enzyme-based cleaners that use amylase and protease, which dissolve starches and proteins, respectively. And then some traditional detergent, which allows oil and water to mix, washes it all away.
The nature of the enzymes are that as soon as they've broken up the starch or protein, they survive the reaction and can happily move onto the next starch or protein molecule. So if they're overactive, without enough targets, then any portion of the dishes that are sensitive to that particular cleaner is going to get a higher "dose" of that cleaner working specifically at it.
This was a particularly bad case of some bagel being cut in half.