RBS850/RBR850 initial connection *requires* router mode

Brand-new RBR850 and three RBS850s. I upgraded the firmware on all units to 4.6.7.13. Configured the router for AP mode, changed the SSID and password, and spent the afternoon trying to get the satellites to connect by pushing the SYNC buttons. They. Would. Not. Connect.

Read a lot of posts here. Factory reset all units so the router was in router mode with factory SSID. Got all satellites to connect. (One of them had a different SSID but the sync-button dance worked.) Changed the SSID and password. Got all satellites to reconnect. Put the router in AP mode again. All satellites reconnected.

I finally got to the configuration I need by not switching to AP mode until late in the process. What should have taken an hour consumed half a day. Thought this post might be helpful for somebody in the same boat.