diff --git a/tracker/tracker/package.json b/tracker/tracker/package.json
index 1ea5ac2bb..00bf42046 100644
--- a/tracker/tracker/package.json
+++ b/tracker/tracker/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@openreplay/tracker",
   "description": "The OpenReplay tracker main package",
-  "version": "3.0.2",
+  "version": "3.0.3",
   "keywords": [
     "logging",
     "replay"
diff --git a/tracker/tracker/src/main/app/index.ts b/tracker/tracker/src/main/app/index.ts
index 91dc20322..3fe006ce8 100644
--- a/tracker/tracker/src/main/app/index.ts
+++ b/tracker/tracker/src/main/app/index.ts
@@ -174,7 +174,24 @@ export default class App {
   _start(reset: boolean): void {   // TODO: return a promise instead of onStart handling
     if (!this.isActive) {
       this.isActive = true;
+      if (!this.worker) {
+        throw new Error("Stranger things: no worker found"); 
+      }
+
+      let pageNo: number = 0;
+      const pageNoStr = sessionStorage.getItem(this.options.session_pageno_key);
+      if (pageNoStr != null) {
+        pageNo = parseInt(pageNoStr);
+        pageNo++;
+      }
+      sessionStorage.setItem(this.options.session_pageno_key, pageNo.toString());
       const startTimestamp = timestamp();
+
+      this.worker.postMessage({ ingestPoint: this.options.ingestPoint, pageNo, startTimestamp }); // brings delay of 10th ms?  
+      this.observer.observe();
+      this.startCallbacks.forEach((cb) => cb());
+      this.ticker.start();
+
       window.fetch(this.options.ingestPoint + '/v1/web/start', { 
         method: 'POST',
         headers: {
@@ -196,7 +213,7 @@ export default class App {
       .then(r => {
         if (r.status === 200) {
           return r.json()
-        } else { // TODO: handle canceling
+        } else { // TODO: handle canceling && 403
           throw new Error("Server error");
         }
       })
@@ -206,26 +223,14 @@ export default class App {
             typeof userUUID !== 'string') {
           throw new Error("Incorrect server responce");
         }
-        if (!this.worker) {
-          throw new Error("Stranger things: worker is not started"); 
-        }
         sessionStorage.setItem(this.options.session_token_key, token);
         localStorage.setItem(this.options.local_uuid_key, userUUID);
-
-        let pageNo: number = 0;
-        const pageNoStr = sessionStorage.getItem(this.options.session_pageno_key);
-        if (pageNoStr != null) {
-          pageNo = parseInt(pageNoStr);
-          pageNo++;
+        if (!this.worker) {
+          throw new Error("Stranger things: no worker found after start request"); 
         }
-        sessionStorage.setItem(this.options.session_pageno_key, pageNo.toString());
-
-        this.worker.postMessage({ ingestPoint: this.options.ingestPoint, token, pageNo, startTimestamp });
-        this.observer.observe();
-        this.startCallbacks.forEach((cb) => cb());
-        this.ticker.start();
-        log("OpenReplay tracking started."); 
+        this.worker.postMessage({ token });
 
+        log("OpenReplay tracking started.");
         if (typeof this.options.onStart === 'function') {
           this.options.onStart({ sessionToken: token, userUUID, sessionID: token /* back compat (depricated) */ });
         }
@@ -254,7 +259,7 @@ export default class App {
     if (this.isActive) {
       try {
         if (this.worker) {
-          this.worker.postMessage(null);
+          this.worker.postMessage("stop");
         }
         this.observer.disconnect();
         this.nodes.clear();
diff --git a/tracker/tracker/src/main/index.ts b/tracker/tracker/src/main/index.ts
index def27c55a..d6c8481df 100644
--- a/tracker/tracker/src/main/index.ts
+++ b/tracker/tracker/src/main/index.ts
@@ -85,6 +85,8 @@ export default class API {
         ? null
         : new App(options.projectKey, options.sessionToken, options);
     if (this.app !== null) {
+      Viewport(this.app);
+      CSSRules(this.app);
       Connection(this.app);
       Console(this.app, options);
       Exception(this.app, options);
@@ -94,9 +96,7 @@ export default class API {
       Timing(this.app, options);
       Performance(this.app);
       Scroll(this.app);
-      Viewport(this.app);
       Longtasks(this.app);
-      CSSRules(this.app);
       (window as any).__OPENREPLAY__ = (window as any).__OPENREPLAY__ || this;
     } else {
       console.log("OpenReplay: broeser doesn't support API required for tracking.")
diff --git a/tracker/tracker/src/webworker/index.ts b/tracker/tracker/src/webworker/index.ts
index 2e9d3b0e0..f61b7bca5 100644
--- a/tracker/tracker/src/webworker/index.ts
+++ b/tracker/tracker/src/webworker/index.ts
@@ -1,4 +1,4 @@
-import { classes, BatchMeta, Timestamp, SetPageVisibility } from '../messages';
+import { classes, BatchMeta, Timestamp, SetPageVisibility, CreateDocument } from '../messages';
 import Message from '../messages/message';
 import Writer from '../messages/writer';
 
@@ -12,8 +12,11 @@ let ingestPoint: string = "";
 let token: string = "";
 let pageNo: number = 0;
 let timestamp: number = 0;
+let timeAdjustment: number = 0;
 let nextIndex: number = 0;
-let isEmpty: boolean = true;
+// TODO: clear logic: isEmpty here means presense of BatchMeta but absence of other  messages
+// BatchWriter should be abstracted
+let isEmpty: boolean = true; 
 
 function writeBatchMeta(): boolean { // TODO: move to encoder
   return new BatchMeta(pageNo, nextIndex, timestamp).encode(writer)
@@ -67,7 +70,7 @@ function sendBatch(batch: Uint8Array):void {
 }
 
 function send(): void {
-  if (isEmpty || ingestPoint === "") {
+  if (isEmpty || token === "" || ingestPoint === "") {
     return;
   }
   const batch = writer.flush();
@@ -82,29 +85,45 @@ function send(): void {
 }
 
 function reset() {
+  ingestPoint = ""
+  token = ""
   clearInterval(sendIntervalID);
   writer.reset();
 }
 
 let restartTimeoutID: ReturnType<typeof setTimeout>;
 
+function hasTimestamp(msg: any): msg is { timestamp: number } {
+  return typeof msg === 'object' && typeof msg.timestamp === 'number';
+}
+
 self.onmessage = ({ data }: MessageEvent) => {
   if (data === null) {
     send();
     return;
   }
-  if (!Array.isArray(data)) {
+  if (data === "stop") {
+    send();
     reset();
-    ingestPoint = data.ingestPoint;
-    token = data.token;
-    pageNo = data.pageNo;
-    timestamp = data.startTimestamp;
-    writeBatchMeta();
-    sendIntervalID = setInterval(send, SEND_INTERVAL);
+    return;
+  }
+  if (!Array.isArray(data)) {
+    ingestPoint = data.ingestPoint || ingestPoint;
+    token = data.token || token;
+    pageNo = data.pageNo || pageNo;
+    timestamp = data.startTimestamp || timestamp;
+    timeAdjustment = data.timeAdjustment || timeAdjustment;
+    if (writer.isEmpty()) {
+      writeBatchMeta();
+    }
+    if (sendIntervalID == null) {
+      sendIntervalID = setInterval(send, SEND_INTERVAL);
+    }
     return;
   }
   data.forEach((data: any) => {
     const message: Message = new (<any>classes.get(data._id))();
+    Object.assign(message, data);
 
     if (message instanceof Timestamp) {
       timestamp = (<any>message).timestamp;
@@ -116,7 +135,6 @@ self.onmessage = ({ data }: MessageEvent) => {
       }
     }
 
-    Object.assign(message, data);
     writer.checkpoint();
     nextIndex++;
     if (message.encode(writer)) {