Jump to slide (previous) doesn't work consistently

Hi Everyone,

I seem to be having problems with allowing a Learner to go to previous slide.  I have 'previous and next' showing on each slide.  Where there is a slide that builds automatically, I found that when I click 'previous' it goes back to the start of the build.  So, I then added a forward and back arrow onto the slide and a trigger to go back to a slide number.  It worked yesterday and then when I checked it again today, it only goes back to the beginning of the build for the slide showing, instead of going back to the slide number I've named on the trigger.  Has anyone experienced similar and if so, how did you fix it?

Any guidance would be appreciated.

Thanks so much

Kay