Course doesn't resume in correctly when exiting Engage interaction

We're having a strange issue with a course we're producing for a client that contains Engage and Quizmaker interactions.

We're producing the course to run on their proprietary LMS, which we don't have access to, and whatever we try we can't seem to iron out some bugs with resume functionality related to 3 particular Engage interaction screens.

In the Player Template Settings we have the course set to resume on restart, with ignore Flash cookies checked, and for the most part this works as we want it to - i.e. the learner exits the course on a certain screen, and when they come back they are returned to the same place in the course.

However, when exiting the course on any one of 3 final Engage interactions in the course, they are not returned to the same place when they return, but according to the client, each of the 3 interactions, when exited, returns them to the same INCORRECT screen every time they try it.

Previously we were having resume issues with every Engage interaction, but we found this was fixed for all but the final 3 by turning off the 'Allow resume' setting in each Engage interaction, which we'd previously enabled at the client's request. We now have 'allow resume' turned off, and the learner can leave the interaction at any time.

We are publishing to SCORM 2004 version 3, so wouldn't have expected this to be an issue related to the suspend_data value being too long, but it IS causing issues on the target LMS. It's made more difficult by the fact that we do not have access to that LMS, and we are unable to replicate the issue; the course runs perfectly well on our own Moodle based development LMS.

Any advice? Would it be possible to upload our source files for you guys to have a look at?