Bookmarking issue

I have been asked to test a project made by another vendor, for one of our clients. There is an issue with the bookmarking where it will prompt the learner the first time, but then jump back to the first slide for the second and subsequent times (after exiting). What might cause this problem and has anyone else seen this behaviour before? I have tested some projects we have built and cannot replicate the issue. It seems to be this one file.

How can I provide this file to support to taker a look at? Presume the attachment button below is public.