I actually think that the answer is yes more often than it is not and I would love to hear your stories. I am especially thinking of "data analysis" with mathematical tools like statistics or network analysis. While the mathematics itself is clearly objective, I argue that often the CHOICE of a mathematical framework, a statistical test, a chosen normalization factor, or similar is where subjectivity comes into play. For statistics, this is a well known fact, with many publications like the famous book by Darrell Huff: "How to lie with statistics". Another point where subjectivity is a big part is in data preparation: what exactly was observed, what is taken into the (data) model, is there a threshold applied to the data to remove spurious data, etc. So, pure mathematic like number theory or graph theory is certainly as objective as it can be. Where is the border line? Tell us your stories of "Subjective math in research".