Oregon instructs me to enter my total reservist pay into Active Duty outside Oregon because I was away for more than 3 consecutive weeks. Then I get an error.

What error are you receiving? TurboTax will ask you to break down the source of your pay—active duty, National Guard or Reservist. Enter the appropriate in-state amounts. If it was all Reservist pay earned out of state, enter $0 for the Oregon in state amounts for Active, National Guard and Reservist.