Spawn Issue

I have found this issue in a few worlds in which i would leave the game in a cave or my mine but when i join back i have spawned in a completely different location there are 2 examples of this i found (unfortunately as with xbox recording is hard and the randomness of the bug i cannot give video evidence of it) example 1: i left the game in a cave and i rejoined in the same x and z co ords but i was at ground level rather than underground. Example 2: i left in my mine and re spawned at the centre of the map around 20 256 1 but i was in the sky above the clouds (assumed to be world limit height) and died immediately the problem being i was in the sky and my mine was as the co ords of around 1300 11 300.