Wireguard oddity

Installing and Using OpenWrt
1

This one I'm not understanding maybe someone can offer some advice.

I'm in the UK and running WireGuard on my router. It's setup for IPv4 only.
My brother is in Nicaragua.

We both run the WireGuard android client from the Play Store.

We noticed this on the site Https://www.carters.com though I suppose it will be apparent for other sites, just not noticed anything yet.

When I load the site from the UK direct it works fine. When I connect on my phone via the WireGuard VPN the site works fine.

When my brother connects to the site from Nicaragua direct he gets directed to a page saying

Sorry, you have been blocked
Your are unable to access carters.com...

When he connects to the site via WireGuard the site loads but the images don't load.

I've tried lowering the MTU (to 1280, even though the site works for me from the UK when using the VPN) but this had no effect.

Any ideas as what could be causing this behaviour?

2

Make sure your DNS in the WireGuard interface on your phone is set to use your router (if that is your DNS server)
Furthermore enable the killswitch on the WireGuard interface on your phone

Indeed slow loading especially of media can be an MTU problem. Set the MTU on both sides (phone and server) to 1280 or try even lower

3

The DNS is set and appears to be working as I can resolve hosts on the OpenWRT network OK, though oddly in temux on the phone issuing an nslookup uses 8.8.8.8

There doesn't seem to be a way to do this on Android from what I can find via google unfortunately.

I am setting this on the OpenWRT side only currently. I'll try on both sides see if it changes things.