@nathanRona I just did a quick test against test.mosquitto.org and was able to publish and receive JSON with Timestamp based values.  I'm posting the JSON config so you can import it and see for yourself.  I can't see exactly what is wrong with your setup but this confirms that it does in fact work.  In the configuration I'm providing there are 2 data points, when you set the value for one it will publish to the receiving topic of the other.
{
  "dataSources":[
    {
      "xid":"DS_b911d1a5-dcfd-424d-ab07-77134185f2a8",
      "name":"Test.Mosquitto.ORG Client",
      "enabled":true,
      "type":"MqttClient",
      "alarmLevels":{
        "DATA_SOURCE_EXCEPTION_EVENT":"URGENT",
        "MQTT_CONNECTION_FAILURE_EVENT":"URGENT",
        "MQTT_PUBLISH_FAILURE_EVENT":"URGENT",
        "POINT_READ_EXCEPTION_EVENT":"URGENT",
        "MQTT_UNKNOWN_TOPIC":"IGNORE",
        "POINT_WRITE_EXCEPTION_EVENT":"URGENT"
      },
      "purgeType":"YEARS",
      "brokerUri":"tcp:\/\/test.mosquitto.org:1883",
      "x509CaCrt":"",
      "clientId":"Mango Automation MQTT Client 148709547341099",
      "userName":"",
      "userPassword":"",
      "topicFilters":"infiniteautomation\/test\/#",
      "autoReconnect":true,
      "cleanSession":true,
      "keepAliveInterval":60,
      "connectionTimeout":30,
      "qosType":"EXACTLY_ONCE",
      "editPermission":"",
      "purgeOverride":false,
      "purgePeriod":1
    }
  ],
  "dataPoints":[
    {
      "xid":"DP_ba31c77f-9c4f-4f02-802c-afcfae830441",
      "name":"number",
      "enabled":true,
      "loggingType":"ALL",
      "intervalLoggingPeriodType":"MINUTES",
      "intervalLoggingType":"AVERAGE",
      "purgeType":"YEARS",
      "pointLocator":{
        "dataType":"NUMERIC",
        "subscribeTopicType":"JSON_WITH_TIMESTAMP",
        "subscribeJsonTimestampPath":"\/ts",
        "subscribeJsonTimestampPattern":"yyyy-MM-dd'T'HH:mm:ss.SSSSSSSSSX",
        "subscribeJsonValuePath":"\/d",
        "subscribeTopic":"infiniteautomation\/test\/number",
        "publishTopicType":"JSON_WITH_TIMESTAMP",
        "publishJsonTimestampName":"ts",
        "publishJsonTimestampPattern":"yyyy-MM-dd'T'HH:mm:ss.SSSSSSSSSX",
        "publishJsonTimestampZone":"UTC",
        "publishJsonValueName":"d",
        "publishTopic":"infiniteautomation\/test\/set\/number"
      },
      "eventDetectors":[
      ],
      "plotType":"STEP",
      "rollup":"NONE",
      "unit":"s",
      "simplifyType":"NONE",
      "chartColour":"",
      "chartRenderer":{
        "type":"IMAGE",
        "timePeriodType":"DAYS",
        "numberOfPeriods":1
      },
      "dataSourceXid":"DS_b911d1a5-dcfd-424d-ab07-77134185f2a8",
      "defaultCacheSize":1,
      "deviceName":"Test.Mosquitto.ORG Client",
      "discardExtremeValues":false,
      "discardHighLimit":1.7976931348623157E308,
      "discardLowLimit":-1.7976931348623157E308,
      "intervalLoggingPeriod":1,
      "intervalLoggingSampleWindowSize":0,
      "overrideIntervalLoggingSamples":false,
      "preventSetExtremeValues":false,
      "purgeOverride":false,
      "purgePeriod":1,
      "readPermission":"",
      "setExtremeHighLimit":1.7976931348623157E308,
      "setExtremeLowLimit":-1.7976931348623157E308,
      "setPermission":"",
      "tags":{
      },
      "textRenderer":{
        "type":"ANALOG",
        "useUnitAsSuffix":true,
        "format":"0.00"
      },
      "tolerance":0.0
    },
    {
      "xid":"DP_0460c207-8a22-4b7c-92b6-ab70c1c41d1c",
      "name":"number-recieve",
      "enabled":true,
      "loggingType":"ALL",
      "intervalLoggingPeriodType":"MINUTES",
      "intervalLoggingType":"INSTANT",
      "purgeType":"YEARS",
      "pointLocator":{
        "dataType":"NUMERIC",
        "subscribeTopicType":"JSON_WITH_TIMESTAMP",
        "subscribeJsonTimestampPath":"\/ts",
        "subscribeJsonTimestampPattern":"yyyy-MM-dd'T'HH:mm:ss.SSSSSSSSSX",
        "subscribeJsonValuePath":"\/d",
        "subscribeTopic":"infiniteautomation\/test\/set\/number",
        "publishTopicType":"JSON_WITH_TIMESTAMP",
        "publishJsonTimestampName":"ts",
        "publishJsonTimestampPattern":"yyyy-MM-dd'T'HH:mm:ss.SSSSSSSSSX",
        "publishJsonTimestampZone":"UTC",
        "publishJsonValueName":"d",
        "publishTopic":"infiniteautomation\/test\/number"
      },
      "eventDetectors":[
      ],
      "plotType":"STEP",
      "rollup":"NONE",
      "unit":"s",
      "simplifyType":"NONE",
      "chartColour":"",
      "chartRenderer":{
        "type":"IMAGE",
        "timePeriodType":"DAYS",
        "numberOfPeriods":1
      },
      "dataSourceXid":"DS_b911d1a5-dcfd-424d-ab07-77134185f2a8",
      "defaultCacheSize":1,
      "deviceName":"Test.Mosquitto.ORG Client",
      "discardExtremeValues":false,
      "discardHighLimit":1.7976931348623157E308,
      "discardLowLimit":-1.7976931348623157E308,
      "intervalLoggingPeriod":15,
      "intervalLoggingSampleWindowSize":0,
      "overrideIntervalLoggingSamples":false,
      "preventSetExtremeValues":false,
      "purgeOverride":false,
      "purgePeriod":1,
      "readPermission":"",
      "setExtremeHighLimit":1.7976931348623157E308,
      "setExtremeLowLimit":-1.7976931348623157E308,
      "setPermission":"",
      "tags":{
      },
      "textRenderer":{
        "type":"ANALOG",
        "useUnitAsSuffix":true,
        "format":"0.00"
      },
      "tolerance":0.0
    }
  ]
}