Room: two connected 'agility training' rooms, once upgraded.

Error: there's a vaulting horse in the background, where a dweller keeps jumping over. It's not possible to select this dweller anymore. Wonder how to stop this dweller from this loop or when/how it will end training at all.

Have you tried selecting the dweller who is in the room via dweller menu?

Well, yes, then she is selected.

But I still can't drag her anywhere else, give her another task, put her in another room, etc. She just wont stop jumping the horse.

But meanwhile I found a workaround.

If I zoom out, that way that the room-view switches from 3D to 2D, the dwellers dont move at all. This was the only way to grab her.

If it happens again you could try going to the room you want her to be in, select it, there should be a little roster emblem on the bottom left corner, click it and you can select an empty space and then select her from the list that pops up. Glad you already found a work around though