How to encrypt logs between Fortigate and logstash

Question

I recently implemented the ELK Stack solution to centralise logs from several devices. It works very well when I send my logs over UDP, but I'm having a few problems encrypting the logs.

Here are some of my logstash inputs :

input {
    udp {
        type => "log-fortinet"
        host => "10.7.7.101"
        port => 5140
    }

    tcp {
        type => "log-fortinet"
        host => "10.7.7.101"
        port => 5140
        ssl_enable => true
        ssl_cert => "/etc/ssl/logstash/logstash-cert.crt"
        ssl_key => "/etc/ssl/logstash/logstash-key.key"
        ssl_verify => "false"
        dns_reverse_lookup_enabled => false
    }

}

Here is the configuration on the FortiGate:

show full-configuration 
config log syslogd setting
    set status enable
    set server "10.7.7.101"
    set mode reliable
    set port 5140
    set facility local7
    set source-ip ''
    set format default
    set priority default
    set max-log-rate 0
    set enc-algorithm high
    set ssl-min-proto-version default
    set certificate ''
    set interface-select-method auto
end

And here is the error message : [ERROR] 2023-10-13 12:30:49.296 [nioEventLoopGroup-2-1] tcp - null: closing due: io.netty.handler.codec.DecoderException: javax.net.ssl.SSLHandshakeException: Insufficient buffer remaining for AEAD cipher fragment (2). Needs to be more than tag size (16)

I work on Ubuntu 22.04.3 LTS

java --version openjdk 11.0.20.1 2023-08-24 OpenJDK Runtime Environment (build 11.0.20.1+1-post-Ubuntu-0ubuntu122.04) OpenJDK 64-Bit Server VM (build 11.0.20.1+1-post-Ubuntu-0ubuntu122.04, mixed mode, sharing)

Hope that someone can help me.