I suspect that Signia HA cannot be repaired after warranty expired. I have a left Pure 7X BTE RIC which is ok. Can I add a Pure 5x 7NX or a 7AX (as a second hand or refurbished HA). Or do the HA need to be of the same model (like both 7X)?
Yes they need to be the same for them to work together, no problem if you want them to work independently, of course you don’t get the full benefit of them this way, as some features require both.
That is what I suspected.