Several years ago, I worked in a very big company. both 2-in-1 box bosses wrote a very unfair evaluation about me dispite my significant contribution to solving a big yield problem, and asked me to sign.
I wrote a big "disagree" and signed my name beneath it.
I later found another postion in a different department.
As long as you are technically strong and feel you are unfairly treated, don't give in. Nevertheless, you should always seek other options in the meantime.
Good luck!