Courses developed in Rise losing learner's progress

We've got a number of courses developed in Rise (our LMS is Kineo Totara, so Moodle-based).  

  

We're seeing a number of users who have completed the course or, in other cases, gotten to the last page (restricted navigation is on, so they can't skip ahead), only to have completion not recorded.  When I've investigated, many of the pages in the module are now unticked, saying they're only, say, 1/3 through, or halfway through.  I have enough cases where I have verified from screenshots that they're at the end - in a couple, I've even 'logged in as' that user, progressed to the last page, and had the progress lost.

 

We have our LMS vendor looking into it, but though I'd investigate from this angle - has anybody seen anything like this?  I can't see any setting in Rise that could cause this.