I can’t remember exactly what its called, but something like router NAT loopback is what you want. I’ll have a look around. But if you set it right, things should work properly. It might be a router setting.
Found it: https://community.tp-link.com/en/home/stories/detail/1726
Never heard that term, but its a very obscure concept, so wouldn’t surprise me if it had multiple names. Probably vender specific names?
Seems quite a few people havent heard of it, hence a lot of the split DNS answers :/