Went to loot chests in Sep City. Had a horse and my bearer with me.
Climbed up the building where you learn the snake dance on the snake dance side. Got the chests at the ghosts. Then worked my way to the top and got the chest up there. Descended the building to the shelter spot with the 2 chests inside and my horse spawned in the entrance to the shelter. This has effectively blocked my path out trapping me inside the shelter.
To the best of my knowledge the horse will stay in the area if the player is still in the area, even on scout. If this was changed I didn’t notice.
The horse can be told to move but the controls are a bit wonky, you need to hit activate key while reticle is pointed where you want the horse to go.
What I would’ve done is just log out for around 5 minutes, this would make the followers think the player was no longer in the area and they would return home.
One more solution that I now use as much as I can: Tell followers to stop following before approaching anything that might corner me. Since followers don’t leave unless you log, (sometimes range can be a consideration) I do my quick business and then return to retrieve them. Sometimes if you can climb the walls this can force them to look for you and thusly clear the way. These solutions are not 100% in every case as there are still situations where you can get pinned or stuck.
Also make sure dismounts have ample clearing space on Both Sides of the horse because you can and will get trapped this way as well. I am absolutely looking forward to the next patch that will fix some of these following issues.
Hope some of these thoughts help as Jim and droch-aon have great ideas posted too!