#1
While fiddling with the new rail system building a turret on the surface of a claimed planet I experienced that, after I exited the core of the turret (R), I couldn't let the planet gravity kick in by pressing the spacebar while pointing at the planet floor. Only after several tries and moving further and further away from the turret I can get gravity back. It seems at least 50 blocks away, but I haven't really counted.
(this happens actually in version 0.19228 release + hotfix, but that version isn't in the picklist.)

Greets,

Jan

A small addition to the above I just noticed. The gravity behavior described happens when initially the turret part with core is build and entered in space, what obviously is needed since construction planet-side isn't really possible. However later, after placement, when the turret core is entered again but now from the planet surface the gravity behaves normal on exiting.

#2
It's unrelated to turrets or rails. It seems to not kick in if your ship is "blocking" you. You stay within the influence of the ship. I exited my ship that was a platform, when the platform was between me and the planet, gravity didn't kick in, only when I went off that platform it worked.