diff --git a/services/IssueService.js b/services/IssueService.js
index b49d420..57dc6bc 100755
--- a/services/IssueService.js
+++ b/services/IssueService.js
@@ -196,6 +196,14 @@ async function handleIssueAssignment(event, issue, force = false) {
     try {
       dbIssue = await ensureChallengeExists(event, issue);
 
+      if (!dbIssue) {
+        const err = errors.internalDependencyError(`Can't find the issue in DB. It's not found or not accessible`);
+        // The dbissue is not found, the db is not accessible, or the issue is still in creation process.
+        // Handle it for rescheduling.
+        await eventService.handleEventGracefully(event, issue, err);
+        return;
+      }
+  
       // Handle multiple assignees. TC-X allows only one assignee.
       if (event.data.issue.assignees && event.data.issue.assignees.length > 1) {
         const comment = 'Topcoder-X only supports a single assignee on a ticket to avoid issues with payment';
@@ -304,6 +312,14 @@ async function handleIssueUpdate(event, issue) {
   try {
     dbIssue = await ensureChallengeExists(event, issue, false);
 
+    if (!dbIssue) {
+      const err = errors.internalDependencyError(`Can't find the issue in DB. It's not found or not accessible`);
+      // The dbissue is not found, the db is not accessible, or the issue is still in creation process.
+      // Handle it for rescheduling.
+      await eventService.handleEventGracefully(event, issue, err);
+      return;
+    }
+
     if (dbIssue.title === issue.title &&
       dbIssue.body === issue.body &&
       dbIssue.prizes.length === issue.prizes.length &&
@@ -347,6 +363,15 @@ async function handleIssueClose(event, issue) {
   let dbIssue;
   try {
     dbIssue = await ensureChallengeExists(event, issue);
+    
+    if (!dbIssue) {
+      const err = errors.internalDependencyError(`Can't find the issue in DB. It's not found or not accessible`);
+      // The dbissue is not found, the db is not accessible, or the issue is still in creation process.
+      // Handle it for rescheduling.
+      await eventService.handleEventGracefully(event, issue, err);
+      return;
+    }
+
     event.dbIssue = dbIssue;
 
     // if the issue has payment success or payment pending status, we'll ignore this process.
@@ -613,6 +638,12 @@ async function handleIssueLabelUpdated(event, issue) {
     await eventService.handleEventGracefully(event, issue, e);
     return;
   }
+  // Sometimes Github send label updated event before issue created event.
+  // This process will be ignored. The label will be processed (stored) at hanleIssueCreated.
+  if (!dbIssue) {
+    logger.debug(`DB record not found. Issue label update ignored.`);
+    return;
+  }
   await dbHelper.update(models.Issue, dbIssue.id, {
     labels: issue.labels,
     updatedAt: new Date()
@@ -629,6 +660,15 @@ async function handleIssueUnAssignment(event, issue) {
   let dbIssue;
   try {
     dbIssue = await ensureChallengeExists(event, issue);
+
+    if (!dbIssue) {
+      const err = errors.internalDependencyError(`Can't find the issue in DB. It's not found or not accessible`);
+      // The dbissue is not found, the db is not accessible, or the issue is still in creation process.
+      // Handle it for rescheduling.
+      await eventService.handleEventGracefully(event, issue, err);
+      return;
+    }
+
     if (dbIssue.assignee) {
       const assigneeUserId = gitHelper.getUserIdByLogin(event, dbIssue.assignee);
       logger.debug(`Looking up TC handle of git user: ${assigneeUserId}`);