diff --git a/frontend/app/player/web/MessageManager.ts b/frontend/app/player/web/MessageManager.ts
index 1eea15095..104a9365a 100644
--- a/frontend/app/player/web/MessageManager.ts
+++ b/frontend/app/player/web/MessageManager.ts
@@ -228,7 +228,7 @@ export default class MessageManager {
         }
         const sorted = msgs.sort((m1, m2) => {
           // @ts-ignore
-          if (m1.time === m2.time) return m1._index - m2._index
+          if (!m1.time || !m2.time || m1.time === m2.time) return m1._index - m2._index
           return m1.time - m2.time
         })
 
@@ -256,9 +256,8 @@ export default class MessageManager {
 
     loadFiles(loadMethod.url, loadMethod.parser())
       // EFS fallback
-      .catch((e) =>
-        requestEFSDom(this.session.sessionId)
-          .then(createNewParser(false, 'domEFS'))
+      .catch((e) => requestEFSDom(this.session.sessionId)
+            .then(createNewParser(false, 'domEFS'))
       )
       .then(this.onFileReadSuccess)
       .catch(this.onFileReadFailed)
diff --git a/frontend/app/player/web/network/loadFiles.ts b/frontend/app/player/web/network/loadFiles.ts
index 8d8142716..888fd257f 100644
--- a/frontend/app/player/web/network/loadFiles.ts
+++ b/frontend/app/player/web/network/loadFiles.ts
@@ -15,7 +15,7 @@ export async function loadFiles(
   try {
     for (let url of urls) {
       const response = await window.fetch(url)
-      const data = await processAPIStreamResponse(response, url !== url[0])
+      const data = await processAPIStreamResponse(response, url !== urls[0])
       onData(data)
     }
   } catch(e) {
diff --git a/tracker/tracker/src/webworker/PrimitiveEncoder.ts b/tracker/tracker/src/webworker/PrimitiveEncoder.ts
index caf0b2db7..ac3e98a03 100644
--- a/tracker/tracker/src/webworker/PrimitiveEncoder.ts
+++ b/tracker/tracker/src/webworker/PrimitiveEncoder.ts
@@ -114,14 +114,4 @@ export default class PrimitiveEncoder {
     this.reset()
     return data
   }
-
-  encodeCompressed(message: Uint8Array) {
-    const length = message.byteLength
-    if (!this.uint(length) || this.offset + length > this.size) {
-      return false
-    }
-    this.data.set(message, this.offset)
-    this.offset += length
-    return true
-  }
 }
diff --git a/tracker/tracker/src/webworker/QueueSender.ts b/tracker/tracker/src/webworker/QueueSender.ts
index 7eff9c662..f46040b3e 100644
--- a/tracker/tracker/src/webworker/QueueSender.ts
+++ b/tracker/tracker/src/webworker/QueueSender.ts
@@ -1,5 +1,4 @@
 const INGEST_PATH = '/v1/web/i'
-
 const KEEPALIVE_SIZE_LIMIT = 64 << 10 // 64 kB
 
 export default class QueueSender {
@@ -32,6 +31,7 @@ export default class QueueSender {
     if (this.busy || !this.token) {
       this.queue.push(batch)
     } else {
+      this.busy = true
       this.onCompress(batch)
     }
   }
@@ -39,20 +39,21 @@ export default class QueueSender {
   private sendNext() {
     const nextBatch = this.queue.shift()
     if (nextBatch) {
+      this.busy = true
       this.onCompress(nextBatch)
     } else {
       this.busy = false
     }
   }
 
-  private retry(batch: Uint8Array): void {
+  private retry(batch: Uint8Array, isCompressed?: boolean): void {
     if (this.attemptsCount >= this.MAX_ATTEMPTS_COUNT) {
       this.onFailure(`Failed to send batch after ${this.attemptsCount} attempts.`)
       // remains this.busy === true
       return
     }
     this.attemptsCount++
-    setTimeout(() => this.onCompress(batch), this.ATTEMPT_TIMEOUT * this.attemptsCount)
+    setTimeout(() => this.sendBatch(batch, isCompressed), this.ATTEMPT_TIMEOUT * this.attemptsCount)
   }
 
   // would be nice to use Beacon API, but it is not available in WebWorker
@@ -80,7 +81,7 @@ export default class QueueSender {
           this.onUnauthorised()
           return
         } else if (r.status >= 400) {
-          this.retry(batch)
+          this.retry(batch, isCompressed)
           return
         }
 
@@ -90,7 +91,7 @@ export default class QueueSender {
       })
       .catch((e: any) => {
         console.warn('OpenReplay:', e)
-        this.retry(batch)
+        this.retry(batch, isCompressed)
       })
   }
 
@@ -99,7 +100,7 @@ export default class QueueSender {
   }
 
   sendUncompressed(batch: Uint8Array) {
-    this.sendBatch(batch)
+    this.sendBatch(batch, false)
   }
 
   clean() {
diff --git a/tracker/tracker/src/webworker/index.ts b/tracker/tracker/src/webworker/index.ts
index 45418d54d..cd32ec5cf 100644
--- a/tracker/tracker/src/webworker/index.ts
+++ b/tracker/tracker/src/webworker/index.ts
@@ -1,9 +1,7 @@
 // Do strong type WebWorker as soon as it is possible:
 // https://github.com/microsoft/TypeScript/issues/14877
 // At the moment "webworker" lib conflicts with  jest-environment-jsdom that uses "dom" lib
-//
 
-import type Message from '../common/messages.gen.js'
 import { Type as MType } from '../common/messages.gen.js'
 import { ToWorkerData, FromWorkerData } from '../common/interaction.js'
 
@@ -103,6 +101,23 @@ self.onmessage = ({ data }: any): any => {
     return
   }
 
+  if (data.type === 'compressed') {
+    if (!sender) {
+      console.debug('WebWorker: sender not initialised. Received auth.')
+      initiateRestart()
+      return
+    }
+    sender.sendCompressed(data.batch)
+  }
+  if (data.type === 'uncompressed') {
+    if (!sender) {
+      console.debug('WebWorker: sender not initialised. Received auth.')
+      initiateRestart()
+      return
+    }
+    sender.sendUncompressed(data.batch)
+  }
+
   if (data.type === 'start') {
     workerStatus = WorkerStatus.Starting
     sender = new QueueSender(
@@ -133,12 +148,6 @@ self.onmessage = ({ data }: any): any => {
     }
     return (workerStatus = WorkerStatus.Active)
   }
-  if (data.type === 'compressed') {
-    sender?.sendCompressed(data.batch)
-  }
-  if (data.type === 'uncompressed') {
-    sender?.sendUncompressed(data.batch)
-  }
 
   if (data.type === 'auth') {
     if (!sender) {