Looking at your credit report,does it say that the loan is in forbearance/deferment? While in deferment, mine showed the minimum payment on the report, but had a notation that the loans were deferred and showed a good payment history each month.
Some lenders will not consider a deferment when they calculate your DTI because they know that you will be making that payment, possibly in the near future. And different lenders have different policies about how to consider deferred loans. Was the loan you were considering going to be paid off before your SLs came due?
That might be a good reason to recon with the lender and see if they change their minds with a manual review.
I wouldn't bother disputing the student loans if they do show that the account is in deferment in the notation, because they are reporting correctly.
