I picke don eo fthese remotes up today and ran into the same problem.
Ive sort of traced it to being 2 'keys' with the same name.
on my surround sound, the MUTE remote button mutes the surround.
I inadvertently added a device option called MUTE, and it did not download (same error) to the remote.
I went back and removed the Mute option i added to the device, and it then downloaded to the remote.

I gather you need to check your custome names closely to make sure they arent conflicting with something else. I would have thought they would have used numerical ID's rather than the actual name as the record.