Recently everyone at work received feedback from colleagues. I received some 'informal' feedback from the area sales director (not my boss) that he feels I don't demonstrate a good understanding of the companies business. When I asked my immediate boss for further explanation or examples, she said it's a perception the director has and he gave no examples. Nor was this documented on paper.
Since then I've been given this feedback on paper but again with no examples, I've been told again it's a 'perception'. I asked whether some of my less experienced colleagues have been given this feedback too, but was told it's confidential.
I have some history of problems with this director, I queried the workload sent my way in the past as it seemed unreasonable and more than others had, he told me to work more effectively and not converse with colleagues 
he also set me up to fail before, when I complained to him about it he said he didn't want to discuss.
As it's a toxic relationship with this bully and I'm due to go on maternity leave soon, should I challenge hid unfair feedback or leave it, knowing that my immediate manager is happy with my performance and hopefully the bully will have moved on by the time I return? He has a history of bullying behaviour but people tend to leave/change departments rather than challenge.