It seems machines (runtime resources & workplaces) are always identified by their host names, regardless of system settings.
In our case our settings were:
register using short names, communicate using FQDN
However, the registration considered short names and FQDN and caused issues after DNS name change that made manual DB updates necessary.
The machines were verified based on their short names in BPAResource and Blue Prism crashed because of FQDN mismatch.
The only reason to chose 'register using short names' is to avoid long FQDN names in Control. Therefore:
1. add settings for short/FQDN in Control that is independent on communication and registration
2. always register and evaluate FQDN and never short names only