Is there a potential for bias when a researcher chooses a topic they personally find interesting?
The short answer is, well, yes. But what alternative would you propose? Forcing researchers to work on topics they aren’t passionate about seems like a bad idea. Academia has few financial incentives as compared to industry. The only reason many stay is because of the freedom it affords them. Take away that, and there’s not much keeping people in it.
Keeping researchers’ biases in check is what peer review is for. Even if you happen to work on a topic you aren’t super passionate about (say, you got moderately involved in a project due to a very specific skill you bring in), you still have an incentive to publish the results, which should be kept in check regardless of personal interest.