RBR50 satelite loses (wireless) connection when turning of DHCP

I do not have proof, but my guess is that the satellite "knows it's a satellite" and requests DHCP only through the backhaul link.  As a test, you could move the DHCP server (temporarily) to one of the router ports.  My (guess again) is that in a similar fashion, the router "knows" that DHCP comes from the WAN port.  Would be an interesting experiment.  (I wait until the wife is out before stringing my 100ft. ethernet cable through the house and up the stairs.) If the DHCP server maintains a log, you could determine if the DHCP server ever received a request from the satellite.

I doubt that the satellite will "work at all" until it receives an IP.  That is sort of an important part of the startup sequence.

There have been several discussions within the last month about Orbi DHCP.  Perhaps you could  private message one of those members?