A surgical instrument includes an end effector, a shaft assembly, a carrier, and a support structure. Shaft assembly extends proximally from the end effector. The shaft assembly defines a longitudinal axis. The carrier is configured to translate the end effector along the longitudinal axis. The carrier includes a carriage, an actuation driver, and an actuation assembly. The actuation driver is configured to rotate along an axis parallel to the longitudinal axis. The actuation assembly is operatively coupled with the actuation driver and the carriage. The support structure includes a supporting portion. The supporting portion is configured to reduce torsional forces exerted on the carriage as the actuation assembly transfers the rotation of the actuation driver into translation of a portion of the shaft assembly to actuate the end effector.