SNMP4J: malformed SNMP v3 trap

Question

I have to send an SNMP v3 Trap to a server using SNMP4J but I can't seem to make it work. With a TCP dump, the remote server guys confirm they're receiving packets but they seem to be malformed in some way.

Code is below:

TransportMapping transportMapping = new DefaultUdpTransportMapping();

        Snmp snmp = new Snmp(transportMapping);

        OctetString localEngineId = new OctetString(MPv3.createLocalEngineID());

        USM usm = new USM(SecurityProtocols.getInstance()
                .addDefaultProtocols(), new OctetString(
                MPv3.createLocalEngineID()), 0);

        SecurityModels.getInstance().addSecurityModel(usm);
        OctetString securityName = new OctetString(username);
        OctetString authPassphrase = new OctetString(authPassword);
        OctetString privPassphrase = new OctetString(privPassword);

        OID authProtocol = AuthHMAC192SHA256.ID;
        OID privProtocol = PrivAES128.ID;

        snmp.getUSM().addUser(securityName, new UsmUser(securityName, authProtocol, authPassphrase, privProtocol, privPassphrase));

        UserTarget target = new UserTarget();
        target.setSecurityLevel(SecurityLevel.AUTH_PRIV);
        target.setSecurityName(securityName);
        target.setAddress(new UdpAddress(agentIp + "/" + agentPort));
        target.setVersion(SnmpConstants.version3);

        ScopedPDU pdu = new ScopedPDU();
        pdu.setType(PDU.SET);
        pdu.setContextEngineID(localEngineId);

        pdu.add(new VariableBinding(new OID(trapOID), new OctetString(
                "beginraisetime:2023-09-10 16:00:00;" +
                        "endraisetime:" +
                        "2023-09-13 15:00:00" + ";")));
        pdu.setContextName(new OctetString("context name"));


        System.out.println("Sending V3 trap");
        System.out.println("PDU: " + pdu);

        snmp.listen();
        snmp.send(pdu, target);
        snmp.close();

I tried to find answers online, there is not a lot of help but I keep reading issues about the Engine ID.. maybe there's something wrong in the way it's generated.