race condition where gather transcribe is restarted after final transcript

lib/session/call-session.js

@@ -877,6 +877,7 @@ class CallSession extends Emitter {
       const taskNum = ++this.taskIdx;
       const stackNum = this.stackIdx;
       const task = this.tasks.shift();
+      task._stackNum = `${stackNum}:${taskNum}`;
       this.logger.info(`CallSession:exec starting task #${stackNum}:${taskNum}: ${task.name}`);
       this._notifyTaskStatus(task, {event: 'starting'});
       // Register verbhook span wait for end