AirPod is connected with phone, but voice call did not connect directly, i have first switch to speaker then switch back to airpod to have conversation, please assist

I am using iPhone XR with AirPod first generation, after latest 13.5.1 OS update, unable to listen or speak while connected to Airpod, to have conversation i need to switch the call to speaker mode then back to Airpod to continue call conversation.

So far i have already re-set the Airpod by forget devise but see no improvement.

Please let me know is there any other setting i have to do or is this something AirPod connectivity issue with 13.5 OS