In what respect?
The first thing students of history learn is that history is an inherently de-centering subject, and thus that the self must be removed before one can begin compiling a work of serious historical study. I believe in the ability of professional historians to examine their own biases and assumptions before setting out to research and write a study. Some people (post-modernists and adherents of Enlightenment era German philosophers, primarily) would argue that it’s impossible to de-center oneself from anything, but I would argue that, if the quest to understand anything outside of our narrow context is impossible, then the people making those arguments should probably just stay home and stare at a wall all day. (This argument does not apply to tools like Eugene D. Genovese, who single-handedly destroyed the ability of scholars to study the intellectual history of the antebellum South; it also does not apply to much of the history written before ~1965)
However, that answer pertains to professional, academic historians. Outside of the realm of academics, historical bias will not be limited because it will always remain a tool of nationalism. I believe I have ranted on here about history textbooks and nationalist historiography before. Another issue is the massive gap between what academic historians know, and what is contained within the mainstream historical canon.
And there are also historiographical issues. Like, a historian may have successfully examined their (for example) patriarchal socialization, but they still could be biased towards a specific historical argument.
Was that helpful? It was a very broad response, but, if after reading it, you have a more narrowed down follow-up question, I’d be happy to answer it. I could write an essay about this, but I think it would be more helpful to figure out what kind of answer you’re looking for before I decide to do that :)