AirPods Disconnecting frequently

I have 1st Generation AirPods .. Lately, they are getting disconnected frequently especially during calls even though they are charged sufficiently.. I use 1 AirPod at a time .. they situation is so bad that I need to oscillate between the left and the right AirPods 2-3 times during a call...

How do I fix this... They haven't been exposed to water damage or physical damage...