People were taking one bug, breaking it in to 3 or 4, then closing all of those.
"Add button for X" became
* "add button on form" * "add CSS for button" * "update CSS for button" * "add CSS files to build process"
Friend of mine took a bug - it was a moderately big one, touched multiple systems, but was a bear to work on. No one else touched it. He spent a few weeks making it work. Eventually closed it. Was reprimanded because his bug-closing stats were bringing down the department's numbers. He was counseled that he should have broken it down in to a few dozen issues, so that he could have closed more and "kept up" with his team mates.
No one else would touch that bug. Most people hadn't been there long enough to decipher how complex it was. But.... they got bigger bonuses because ... bug closing numbers.
We all probably have similar stories to share, and I know the "what gets measured gets gamed" mantra.
It's still frustrating to know that this mentality infects so many professional "thought workers".