Branching problem

I suspect this sort of question has been asked and answered many times, but my searches turned up nothing, so I ask.

The crux of the problem seems to be a conflict between BRANCHING and RESTRICTED navigation.

I've attached a PDF of the branching scheme we need. Notice that number 2 is a decision branch that takes the student through one set of slides or another depending on the decision they make.  Branching worked perfectly until I restricted navigation.

With navigation restricted (and first time through the set)  when the student makes either choice at #2 they are taken to the correct slide next, BUT when they click next on that slide the "BACK ONLY" message appears. The only way that I have found to get around this problem is to go back to the #2 decision and select the OTHER option. Doing so clears the message and allows me to proceed, BUT we do not want students to do this.

The paragraph above seems a bit vague, so I will describe it more concretely.

Start with #1, click NEXT and go to #2. There you click hyperlinked button A (takes you to slide 3) or hyperlinked button B (takes you to slide 4). On either of these slides clicking NEXT does not take you to slide 5. Instead the BACK ONLY message appears and the student cannot proceed.

Assuming I had initially clicked hyperlinked button A and navigated to slide 3, if when the BACK ONLY message appears, I clear the error message, click the BACK button of the Articulate skin, return to slide #2, then click hyperlinked button B, and visit slide 4, I can then navigate on to slides 5 and 6.

Does anyone know of a way around this apparent problem of mutual exclusivity between custom branching and restricted navigation?

Thanks