suggest to contact tp-link support team on support@tp-link.com, they seem to have a beta firmware for the VOIP

josuer wrote The connection on other smartphones works fine. I have a WA801ND and is up to date, I already checked the firmware and it's the last build according to tp-link's site. The repeater has...

suggest to change the channel, bandwidth on the access point, if still have any issue. contact with tp-link support team on support.uk@tp-link.com for further analysis

What's the firmware version and hardware version of them .Suggest to update firmware to the latest first, change channel

No

It is not suggested to use a second extender connect to the first extender, as far as I know , extender works on half-duplex, speed will be half of the main router If you used the second, the speed...