Check Gurobi redundant constraints
Your statements are somewhat contradictory: If gurobi was to add redundant constraints in the beginning, the presolve step would remove them again and second them being redundant would mean that they wont influence the solution. Thus, there would be a modelling error on your side. 
As sascha mentioned it is extremely unlikely that any constraint-generating routine/presolve step would be falsely implemented - such errors would show up immediately, that is before patching into the published versions. 
And from a theoretical side: These methods require mathematical proofs that guarantee they do not cut-off feasible solutions. What is overseen sometimes, I did that only recently, is the default lower bound of 0 on all variables which stems from the LP-notation according to standard form. 
Further investigation can be done if you were to post the .lp and .mps files of your initial problem with your question. That way people could investigate themselves.
Is there any way to check whether Gurobi is adding an extra redundant constraint to the model? 
I tried model.write() at every iteration and it seems fine. But still, my output is not what I'm expecting. 
I want to check whether there are any unwanted constraints added by Gurobi when solving.