When going through a Nether portal, a player frequently spawns not where he should, but inside a wall close to the corresponding portal and starts to take suffocation damage (obviously😃). The game does that in both cases: when a player goes through a portal for the first time (the portal must be generated in the dimension player heads to) and when both portals (Nether and Overworld) are already generated.
Have fun fixing that :PP
And good luck <3
Environment
Windows 7, Java 7 update 60 (build 1.7.0_60-b19)
8GB DDR3 RAM, Intel Core i5-4570 (3.2 Hhz)
Gigabyte GeForce GTX 750Ti (2GB GDDR5)
But probably doesn't matter in this particular case 😛
Duplicate of MC-73504.