The RPID is placed in clientData, and a hash of client data is passed over CTAP2 to the key. Ā So that any security key would error directly based on the RPID.
In the case of a discoverable credential, the RPID is passed as a string but as this is on Authenticate that seems unlikely to be the problem.
My guess is that it is some sort of TLS validation issue related to what is going in client data.
Can they use the same authenticator with Chrome to authenticate at the RP if make credential works?
I donāt know what level your library is at. Ā If it is talking HID to the key then perhaps something is happening and it is loosing state and there is a HID error. Ā However that would not likely be dependent on RPID. Ā Those are the two places that I can think of some sort of name error happening.
John B.