You specify an endpoint, WireGuard will take that endpoint and route it via its WAN to escape the tunnel that is the normal modus operandi.
I concur with @psherman that it could be the endpoint not resolving to a public IP address.
Alternatively your WG interface does not have an address (I know there are some which say you do not need it and sometimes it will work without but I have seen strange things coming from the lack of an IP address)
Maybe it is the lack of the IP address which is causing you this trouble?
I would start by giving your WG interface on both side an ip address: list addresses '10.10.10.1/24' on one side and list addresses '10.10.10.2/24' on the other side (the WG subnet must be different from all other subnets on both sides)
You should also allow 10.10.10.2/32 on the ip address 10.10.10.1/24 side
(list allowed_ips '10.10.10.2/32) and 10.10.10.1/32 on the 10.10.10.2/24 side (list allowed_ips '10.10.10.1/32)
Reboot afterwards.
If that does not help than remove the endpoint, you actually only need an endpoint on one side.
If that solves the problem it is the endpoint not properly resolving.