RST after client hello

Yes, I tried with the Curl command as well. It was reporting "unknown SSL protocol error". I tried to initiate the connection using the openssl command and tried to force it with different TLS versions (1.0, 1.1, and 1.2) and sent SNI, but still no luck.

SSL handshake only fails for the custom port, but when I initiate using 443, it works fine from F5 (Curl, openssl, and health check).

[Active:Changes Pending] log # openssl s_client -connect x.x.x.x:custom_port -servername example.com
CONNECTED(00000003)
write:errno=104
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 0 bytes and written 276 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
    Start Time: 1753690172
    Timeout   : 300 (sec)
    Verify return code: 0 (ok)