contains(., "SF215FMT-05") should not be true unless @DROPID contains the entire string "SF215FMT-05," so the behavior you describe is not expected. The first formula you described should also work if @DROPID is exactly "SF215FMT-05". Have you tried displaying @DROPID in your form and making sure it has the values you think it does?
One other thing you might try is displaying the d:ROUTELOG fields in a repeating table or section (if you're not already), and adding two expression boxes with the formulas @DROPID = "SF215FMT-05" and contains(@DROPID, "SF215FMT-05") to see where the formulas are true and where they are false.