Radius stopped working on high sierra server, possible permissions problem?

Radius on my Mac Mini running MacOS Server Version 5.6.1 (17S2109) stopped working.

In Radius' LOG I get:

Sat Feb  9 18:44:20 2019 : Error: TLS Alert read:warning:close notify
Sat Feb  9 18:44:20 2019 : Error:     TLS_accept: failed in SSLv3 read client key exchange A
Sat Feb  9 18:44:20 2019 : Error: rlm_eap: SSL error error:140940E5:SSL routines:SSL3_READ_BYTES:ssl handshake failure
Sat Feb  9 18:44:20 2019 : Error: SSL: SSL_read failed in a system call (-1), TLS session fails.
Sat Feb  9 18:44:20 2019 : Auth: Login incorrect (TLS Alert read:warning:close notify): [SOMEONE/<via Auth-Type = EAP>] (from client SOME NAME port 0 cli ***some address***)

The server has an SSL certificate running from StartCom which is still valid!

Upon trying to troubleshoot I found out that there might be problems with permissions. I run an OpenDirectory Server.

When investigating it I get:

[~]$ sudo /usr/libexec/slapd -Tt
Password:
5c5f121d bdb_monitor_db_open: monitoring disabled; configure monitor database to enable
config file testing succeeded
[~]$ slaptest -f /private/etc/openldap/slapd.conf -v
5c5f1224 could not open config file "/private/etc/openldap/slapd.conf": Permission denied (13)
slaptest: bad configuration file!
[~]$ sudo slaptest -f /private/etc/openldap/slapd.conf -v
5c5f1230 bdb_monitor_db_open: monitoring disabled; configure monitor database to enable
config file testing succeeded
[~]$ 

Which is rather strange since it should output the state of the OD Server ...

I updated brew and upgraded all cellars, but had to install new Xcode before.

Quite strangely when trying to run

brew prune

I get:

[~]$ brew prune
Error: Calling 'brew prune' is disabled! Use 'brew cleanup' instead.

What could that be? How can I:

A) repair permissions.

B) get RADIUS running again.