This is a known issue.
The main issue is the stasis and revelancy game mechanic that is built directly into unreal engine.

The quick answer is, just do a mass whistle to disable wander just before you log off or know you are going to be going out of visual range of the dino pen.
With the new whistle grouping, this should be much more manageable than before.

What I would need to do to stop this is somehow change the value on my parts so that they have a larger value for when the game decides they pop in and out of visual range.
dinos and some of my doors are skeletal meshs, they stay in range longer than static meshs.
The diff is anything skeletal has animation and or AI / ability to be a controlable character.

Basicly, the statis node is a single un measureable point in the game, the size of say a grain of sand.
This point I have set to be at the exact center of the circular area.
So the game uses a distance as a default value set by the actual base code it seems, there are a few spots that seem like it might be editable values for adjusting this, but so far tweaking them, does not show any noticable changes, so this may be in fact, locked as a setting from the main programers.

So, lets say as an example, a structure despawns from view at 10,000cm.
and my domes nearest wall to the players camera is at 9,999cm
Logically that bit of the wall shoudl become visible.

But the game does not work this way.
When the statis node of a structure becomes that 10,000cm units away from the camera is when the structure will re appear in full.

Now the reason animals escape:
Since the distance of my domes horz area is either 2500cm radius, or 5000cm dia, what ever value makes more sense to you.
that means, the actual distance for it being registered as a collision wall for holding wandering dinos is reduced by that 2500cm, cause of the difference between the visual body and the statis node.
This system seems to be setup so that it works very well with smaller peices, that have the statis node placed inside a non viewable / reachable volume, I.E. inside a walls thickness.

So, if you drew a line to where the center of my foundations circle is from where you are standing, and divide the circle in 2 halfs. where the half line is perpendicular to the view projection line.
anything with a statis node in the closer circle half will appear before my wall, anything in the farter cirlce half will appear after.

But, for the farther circle half, since dinos are sketal mesh, and have a higher priority, when you move into visual range VERY! fast, the dinos will spawn first, since they, get revealed at top of the order stack.

With a fast pc and fast internet connection, that usualy is not an issue but if you actually get lag in the game, it can be an issue.

To anyone that understand this more technical mathmatical reason, I hope this clears some things up.