Hey, thanks for your thoughts. The file is ported up from 2013. It is big 65MB or so. I went back to an earlier version of the file which was small but also ported up from 2013 and had the same behavior. I tried creating a new file and simple floor plan and the walk through worked fine, stopping and not returning to the initial view.
Later today working on the original job, it moved as it should. I might well have some corrupt objects as this file has been in progress for a long time, through many variations of design. It was, in fact, begun in VW 12.5!