Hello everyone,
I'm using the IoT Library to implement the MQTT communication with my local broker server in order to publish and subscribe at specifics topics to share and consume information about my application. But, it seems that are occurring some memory leak problem in a "high" frequency (more than 10 Hz) subscribe process.
I follow the same method as in IoT Lib exemples, and at first looks perfect but my PLC was rebooting frequently and when I check its memory usage that was increasing as fast as the subscribe massage was sent.
I'm using a WEG PLC410 and a WEG PLC500, and this error occurred in both of them (including in CODESYS Control Win x64). The application sends to the system a message JSON with the float payload Ex. {"data" : 0.8500}, but this happens with a INT, or BOL as well.

I use the follow code in my application to find the value:

//FindFirstValueByKey VARs
PROGRAM JSON_VELO
VAR
//------Setting the JSON Subscriber to Set the Relay Value
  jsonDataVelo          : JSON.JSONData;
  jsonByteArrayReaderVelo      : JSON.JSONByteArrayReader;
  xST1okVelo            : BOOL;
  FindFirstValueByKeyVelo      : JSON.FindFirstValueByKey;
  jsonElementVelo          : JSON.JSONElement;
  xDoneReaderVelo          : BOOL;
  xDoneFindVelo          : BOOL;
//STRING and WSTRING for Subscribe the massage  
  sPayloadJsonVelo   : STRING := 'opa';
  psPayloadJsonVelo  : POINTER TO BYTE := ADR(sPayloadJsonVelo);  
  //wsPayloadJsonRelaySet   : WSTRING := "opa";
  wsPayloadJsonVelo   : WSTRING := STRING_TO_WSTRING('opa');
  pwsPayloadJsonVelo  : POINTER TO WORD := ADR(wsPayloadJsonVelo);
  lrVelo        : LREAL;
  xKeepAliveVelo    : BOOL;
  xSetVelo      : BOOL;
  RSSet        : RS;
  LIMPAR        : STRING;
  //Find the msg end
  sFindVelo       : STRING := '}';
  psFindVelo       : POINTER TO STRING := ADR(sFindVelo);
  iLenVelo      : INT;
  iSizeVelo       : INT := 12;

udiContMsg      : UDINT;
END_VAR

// FindFirstValueByKey CODE
// Relay Set configuration
xSetVelo := MQTT_SUBSCRIBER.RSVelo.Q1;
IF xSetVelo THEN
  xKeepAliveVelo := TRUE;
END_IF
IF xKeepAliveVelo THEN
  udiContMsg := udiContMsg + 1;
  iLenVelo := TO_INT(StrLenA(psPayloadJsonVelo));
  iSizeVelo := iLenVelo - TO_INT(MQTT_SUBSCRIBER.udiPayloadSizeVelo);
  StrDeleteA(psPayloadJsonVelo,iSizeVelo,iLenVelo);
  wsPayloadJsonVelo := STRING_TO_WSTRING(sPayloadJsonVelo);
  pwsPayloadJsonVelo := ADR(wsPayloadJsonVelo);

//MQTT.ConvertUTF8toUTF16(sourceStart:= ADR(sPayloadJsonVelo), targetStart:= ADR(wsPayloadJsonVelo), dwTargetBufferSize:= TAM, bStrictConversion:= 1);
  //Reset jsonByteArrayReader
  jsonByteArrayReaderVelo (
                xExecute   := TRUE,
                pwData     := pwsPayloadJsonVelo,
                jsonData   := jsonDataVelo,
                xDone     => xDoneReaderVelo
                );
  FindFirstValueByKeyVelo(
                xExecute   := xDoneReaderVelo,
                wsKey     := "data",
                diStartIndex:= 0,
                jsonData   := jsonDataVelo,
                jsonElement => jsonElementVelo,
                xDone    => xDoneFindVelo
                );                
  IF   xDoneFindVelo THEN
    lrVelo := jsonElementVelo.value.lrValue;
    //Reset jsonByteArrayReader
    jsonByteArrayReaderVelo (
              xExecute   := FALSE,
              pwData     := pwsPayloadJsonVelo,
              jsonData   := jsonDataVelo,
              xDone     => xDoneReaderVelo
              );
    FindFirstValueByKeyVelo(
                xExecute   := FALSE,
                wsKey     := "data",
                diStartIndex:= 1,
                jsonData   := jsonDataVelo,
                jsonElement => jsonElementVelo,
                xDone    => xDoneFindVelo
                );  
    xKeepAliveVelo := FALSE;
    GVL.xSetVeloRead := TRUE;
  END_IF
END_IF

And this to subscribe at the topic:

//SUBSCRIBE VAR:
//----------------- Subscribe Velocity -----------------------
  MQTTSubscribeVelo    : MQTT.MQTTSubscribe;//Variable MQTTSubscriber block -X - function-X
  wsTopicSubscribeVelo   : WSTRING(1024) := "CORE/odometry/GET/data/simp"; // Topic to publish a message
  sSubscribeMassageVelo  : STRING;
  udiPayloadSizeVelo    : UDINT;
  xSDoneVelo   : BOOL;
  xSErrorVelo   : BOOL;
  xReceiveVelo      : BOOL;
  eSTypeVelo   : MQTT.MQTT_ERROR;
  eSMQTTErrorVelo      : MQTT.MQTT_ERROR;
  RSVelo          : RS;  
  udiCont          : UDINT;

//SUBSCRIBE CODE:
MQTTSubscribeVelo(
        xEnable:= MQTT_CLIENT.xConnection_Broker AND NOT xSErrorVelo AND NOT JSON_VELO.xKeepAliveVelo,
        pbPayload:= JSON_VELO.psPayloadJsonVelo,
        udiMaxPayloadSize:= SIZEOF(JSON_VELO.sPayloadJsonVelo),
        udiPayloadSize => udiPayloadSizeVelo,
        mqttClient:= MQTT_CLIENT.ClientMQTT,
        wsTopicFilter:=wsTopicSubscribeVelo,
        xDone => xSDoneVelo,
        xError=> xSErrorVelo,
        xReceived => xReceiveVelo,
        eMQTTError=> eSMQTTErrorVelo
        );
        RSVelo(SET := xReceiveVelo, RESET1 := JSON_VELO.xKeepAliveVelo);

which version are you using? is this latest available version?