You are probably aware that there is risk associated with manually updating to firmware that Netgear is not ready to "announce" on the app and web interfaces. People report that this firmware has fixed several issues that appeared when 2.5.0.38 was released.
There are two separate firmware files, for the router (RBR50) and for the satellite (RBS50)
When doing a manual update, the user has to connect to the web interface of the device to be updated.
i.e. To update the router, connect to the router. To update the satellite, connect to the satellite, and "Firmware Update" is the bottom item on the Home Page menu.
The satellite does not have a "name" (like "orbilogin.net") Look on the Attached Devices page to learn the IP address of the satellite, then open another tab on the web browser and connect to "http://<ip of satellite>" with the same credentials ("admin" and the Orbi admin password).
Were you connected to the satellite when it rejected the firmware file?
Well this is just strange. I have not seen comments about the firmware files not loading. Lots of people seem to have installed 2.5.1.8
Probably time to open a new post with a topic like RBS firmware 2.5.1.8 file not accepted. (People tend to quit reading posts when they get fairly long, and a new post draws attention better.)
Caveat: I have not loaded 2.5.1.8 yet. I am still "fat, dumb, and happy" on 2.3.5.30 and don't plan to mess with my Orbi until January.
