AutoNotification Whatsapp - Voice Call

Voice calls over Whatsapp used to have a Vibration alert, but now due to a bug this does not happen on certain phones like mine even after all vibrate settings are turned ON. So when there is an incoming call over Whatsapp, it shows up on screen but the phone does not vibrate in silent mode. This can be very difficult when your at office or in a meeting where you cant have your phone in general mode. So to solve this issue I tried using the "Autonotification - Intercept" to detect Incoming voice call text using the %antext and added a Vibrate task when the matching text is intercepted. But the problem is that the vibrate task is set to run for 30s so even if I answer the call, the phone keeps vibrating for full time set. I want the vibrate task to stop as soon as I answer the call. How do I do that, please help as I am missing a lot of calls due to this bug and I know tasker is my best option.