The first is likely due to the Javascript within the WebRTC client on the browser. The second may be just that, that it failed to connect. You’d need to dig deeper for both.
Then investigate it further. Look at the address it is attempting to use. Check the Javascript console. Attempt to connect and verify the system can indeed connect. Do packet captures.
No? The problems are from the Javascript and appear to be from before a call is even initiated, unless you are now referring to a different issue. STUN doesn’t help with that.
I had tried with different browser version and updated the version and check but no solution & I had checked the console log but that will not help for me to overcome this issue