Recently a new manager has joined our team, and I learned from him that a coworker told him I was not doing part of my job that I was in fact doing. I do not know which coworker said this, but one has a much higher probability of being the source. I also learned he had told my previous manager this, but my previous manager never talked to me about it.
When my new manager brought it up he was upset with me. Later when I presented the evidence that I was in fact doing the part of my job my coworker, my manager's attitude changed to it happened in the past so it doesn't matter anymore.
My concern is two-fold, if my coworker is lying about me and apparently my old manager simply took the lies at face value, I do not know who else in the office he has lied to about me.
Second, it seems as though my manager thought that part of my job mattered greatly when he thought the feedback was true, but then it no longer matters once the feedback is false. Personally I would think a manager would be upset at the idea of receiving false feedback.
My question is how do I deal with this situation? Should I attempt to gently confront the coworker in question? If it seems like my manager has made up his mind about me (regardless of whether the evidence was true or not) should I just switch teams? I'm concerned that just switching teams will cause my manager to cement his view on me, is this a valid concern?