I was given a bottom ranking one year, when the previous year (in the exact same role - no requirements had changed), was ranked the highest employee on the team - received an additional bonus even for being the highest.
We had no new-hires onto our team, so literally, there were no changes to the team between the yr I rec'd the top rank vs. the following yr, when I received the bottom rank. The following yr when I got my bottom ranking, no performance issues had ever been discussed or documented/emailed in my mid-year. Nada. Nothing.
No emails/documentation throughout the entire year even before or after my mid-year, stating my work was anything less than what was needed for my role. And then I'm told in my end of year eval that I'm lowest ranked. I have no idea where it came from. But it gets worse - I was never put on a pip after receiving the low ranking and bad review, to help identify what exactly I needed to improve.