I would do a clean install and setup on the Slate AX, do not save settings or packeages and do not use a saved config file. When you start wgclient it tries to us Ipv6 to resolve but can’t and starts the process again.

It also seems that the tp-link is multicasting to the Slate AX.
The Slate has a issue Tx/Rx on Channel 2 with bandwidth set to 20/40.
Try another channel and set bandwidth to 20mHz

The Slate AX is disconnecting but I think it is a config error possible do to Firewall 3 to Firewall 4 again.