The fix for
MC-100410 introduced a height limit for teleportation, this affects the /tp and /teleport command. The problem is that the height limit is currently lower than the /summon height limit (30.000.000). This means you have to summon an entity at 30.000.000 and then teleport to it instead of just teleporting to 30.000.000.
The expected behavior would be that the height limit for teleportation would be -30.000.000 respectively 30.000.000 as well since that is a rather low value compared to the ones in
MC-100410 and therefor would only cause problems which would appear at x / z 30.000.000 as well.