On a one-line diagram, a vertical bus panel should have horizontal branch breakers--NOT vertical!
When you generate a one-line diagram, if you have panels that have a vertical bus, their branch breakers end up at the bottom of the bus and are vertical. The look like main breakers--not branch breakers. A work around for this is for every vertical bus panel, generate a riser diagram starting with that panel. Even this work around is not perfect, as you have to resize the vertical bus and fiddle with the branch breaker.