Apply systemd sandboxing by default to some services

sdwdate is getting killed on Debian buster on the ppc64el architecture.

How to debug systemd hardening? All I get:

sdwdate.service: Main process exited, code=killed, status=31/SYS

Any way to see a more specific error message which systemd hardening was violated? Any other way to debug other than trial and error which the offensive option is?