I had the same problem finishing the same jail. When completing the wood door frames, a cart of stone became locked in place within the frame. I could not select it. Later, after the iron gates were put in, It became selectable, but not reachable. Trying to connect the horse to it or remove stone caused my character to run outside to the closest wall point.
@Roccandil I had that same problem occasionally. The "gathering bar" would pop up and then close as if I had moved. I found that if I went off and gathered other herbs, I could go back and eventually gather that one.
Not sure if this is a bug or intentional, but when I requested to become a city citizen, it used my account name rather than the character name. Would that make multiple characters citizens, if we are even allowed more than one after testing phases?