It's happened a few times now... Tamed mounts hanging out back at base and you are in a distant biome travelling some place on a different mount. Suddenly, without warning, a tamed mount that was back at base suddenly spawns right next to you!!!!! What is going on devs?!
#Tamed Mounts Magically, Spontaneously Transporting to Current Location
sleek pelican
exotic fable
This happens if
a) the mount is set to follow (it'll teleport to you if you're getting too far in front)
b) the mount is falling through the world (this as an alternative to your mount disappearing completely)
Mounts falling through the world is an annoying and persistent issue
The mount loads in before the ground loads in - thus it falling through the world
When you're more than 1000m away from your base, it unloads from active memory (after all, you don't want the entire map an all animals and such loaded into active memory - the performance drain would be massive)
Now when you get back within 1000m from your base, it'll load everything back into active memory; but loading things in takes time
They've already made it so that building pieces load in before the mounts load in - so if you have your mounts on floors or foundations, it shouldn't be an issue
However, if you have your mounts walking around on the ground, the mounts may load in before the world itself has loaded in - resulting in your mounts falling through the world and disappear forever
When this happens and the owner of the mount is online, the mount will teleport to the owner
Sure it might be inconvenient, but if the alternative is losing your mount completely...
sleek pelican
In my case, I think we've had both a) and b) happen to us at some point.
Makes perfect sense what you've said actually. It immediately explains why one of our horses was a few meters under the ground (too far to mount it and use 'unstuck'). The horse did eventually show up 200 meters outside of the base after a couple of days.
My original point is likely to be (a), though. Most probably the mounts in question had been set to "follow" and our base is completely enclosed. It was in grasslands biome of Prometheus. And it suddenly teleported to me when I was halfway through the swamp on the way to Ashlands. I didn't know they had a teleport set up. Makes sense now.
Will ensure I set to "Stay" and "Passive" in future.