Is there a screw missing from the right dropout?
No, only the cover is missing. The hole is only needed for Stromer with the older TMM sensors P178 and P211 (Gen. 2). The sensor plate is mounted there with 3 screws in the dropout. The latest P218 sensor only has 2 screws for mounting. The superfluous hole in the dropout is covered with a rubber cap.
See also TMM-SENSOR - 'Sensor types'
See also OMNI / Display V1, V1.1 - 'Omni flow chart'