I've come upon this problem in one of my game where I was trying to delay the start of a walk with an event. Essentially, if you save or undo at the right moment, the walk breaks and never (re)starts.
I don't know if I'm trying to do something that wasn't meant or if this should be logged as a bug. Anyhow, check the following taf and follow instructions to the letter when they are shown. Type "Start" to initiate.