A bug/glitch/idk which stops me from joining single-player worlds

What happens is, whenever I try to join my single-player world I get this "err connection timed out." (Image should be somewhere don't know how this works that well) note that this ONLY effects my single player worlds, I can still join friends worlds and servers, just not my own.

how to replicate? I just press my world icon it freezes on loading resources for a bit then get the err "connection timed out." Message.

i don't know what causes this exactly but it may be a hardware issue but I'd thought it best tofu report it here anyways. (Edit: forgot to mention that if I switch WiFi off I can join my worlds again)