All the IAP should have the same Firmware, i mean the same version. The IAP 103 didnt update to the same firmware as the others becasuse it uses another firmware differnetes as 105 and 93
First sorry i didnt read that you had another cluster going, and you wanted to insert this instant to the cluster, i though it was a new cluster you need to do. Have in mind that if you got a cluster, the config should download itseft of the master if it correctly done.
Secondly they need all to the in the same regulatory domain otherwise it wont join the cluster
Third yes it will affect the roaming from the 103 to the other cluster and vice versa as they are NOT communicating
I recentrly got a call from a client with this same issue, as he had to config a new cluster, at the beggining he said the same, i cannot see the SSID when putting PA(our country code) but PA as you see in the list i gave you before its on the regulatory domain supported. I asked him to upgrade it to the lastest firmware which fix this. And the other option as well was changing it from regulatory domain.
In your case, i what i would do is this
1-Disconnect the IAP 103
2-Go to the console of the clusters of IAP 93 & 105 create a backup of the config
3-Upgrade to the lastest firmware the IAP 93 and IAP 105
4-When they are done, do a backup of the config
5-Connect this IAP 103 and upgrade this one to the lastest firmware
6-At the end they should all have the same code but they will have a different class of firmware(there is pegasus, Orion etc etc(dont remenber which one is the 103)
7-The AP will reboot and download the config from the Master.
After that they should hopefully see each other and you hopefully should see the SSID from the IAP 103( as i told you before this happened to me a few days ago) and i as said the other option which was upgrade the firmware
The upgrade should work as the AP isaw it was on the list of aps with compliance https://pctools.arubanetworks.com/compliance/
For more information about this common problems of IAPS joinnig a cluster please go and see this video
https://www.youtube.com/watch?v=4s70LKIHrfs
Its really have good info
Cheers
Carlos