I have a pen setup that has it's own path nodes that are not connected to the nodes outside of the pen. So the animals shouldn't even attempt to move out.

But if I wait for a few hours the creatures will sometimes appear outside of the pen. And just now, I had my horse stood nearby and after waiting my horse was trapped inside the pen.

Is this a landscape issue?

I altered the terrain to make the ground flat for my pens. I have made sure all pathnodes are on the floor where I altered the land etc.

Anyone got any ideas?

Happens all the time. All the MMM animals eventually end up outside their pens.

The horse you probably won't be able to prevent ending up in there, but the animals you may be able to keep in the right place by adding a marker in the middle of the pen and making sure their wander package keeps them within a certain distance of it.

The game simply seems to ignore obstacles when calculating wandering during times that gamemode isn't "active".

If you really want them in there, and the wander package restriction doesn't work, you'll need to script them to disable, moveto and reenable if they're outside your desired area.

Thanks, I used the MoveTo command. Works fine now.

A lot of it seems to be related to how the pathnodes are setup. When people place nodes, they have a tendency to place them too close to the fence line on either side. Since the game tends to move actors to the nearest node when being loaded, actors wandering to one point are often moved to the nearest node outside the room since that node is closer than other points. But, if you leave a space of about 128 units away from the fence, and don't put any nodes closer, things will normally stay inside.

Another way, if you never intend to have any NPCs travel from outside in, or inside out, is to enclose the pen in a subspace.