Next revision always "B" in revision table?

I have noticed something unusual recently.  When selecting the next row (next revision) on our revision tables we no longer see a prompt for the next consecutive letter as we used to.  See this image:

It makes no difference whether I am starting (as in this image) or going from a rev "D" to rev "E".  The prompt always shows "B".

Am I missing a SW setting somewhere that can have the prompt display the next revision?

SolidworksDrawings And Detailing