Social Security should not be withheld for Railroad employees. Railroad employees are not covered under Social Security. Boxes 3, 4, 5, 6, and 7 of Form W-2 apply for employees covered under the Federal Insurance Contributions Act (FICA) and should be blank for railroad employees.
Did you enter RR Tier 1 and Tier 2 in Box 14? If so, it should not cause any problems, as box 14 is informational only. You can choose the 'Other' category for these box 14 items.