Remotely Monitoring RDP Certificate

Question

We use OpenSSL on a CentOS 6 server to monitor the certificate on servers for RDP.

To do this we use:

openssl s_client -connect SERVER01:3389 -prexit

This has worked flawlessly until 4 days ago, when it suddenly stops showing that a cert is used and instead shows the following for a single server:

CONNECTED(00000003)
140439032170136:error:140790E5:SSL routines:ssl23_write:ssl handshake failure:s23_lib.c:177:
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 0 bytes and written 305 bytes
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
    Protocol  : TLSv1.2
    Cipher    : 0000
    Session-ID:
    Session-ID-ctx:
    Master-Key:
    Key-Arg   : None
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    Start Time: 1539710511
    Timeout   : 300 (sec)
    Verify return code: 0 (ok)
---
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 0 bytes and written 305 bytes
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
    Protocol  : TLSv1.2
    Cipher    : 0000
    Session-ID:
    Session-ID-ctx:
    Master-Key:
    Key-Arg   : None
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    Start Time: 1539710511
    Timeout   : 300 (sec)
    Verify return code: 0 (ok)
---

I have seen that older versions of OpenSSL caused this error, but since the version hasn't change (1.0.1e) and it was working, I cannot see what is wrong.

I've also tried resetting the server's RDP cert, but again no change.