Submit button not appearing in second of two consecutive drag and drop activities.

I have two modules of 10 that have drag and drop activities with submit buttons on the play that will not show on the player when published to LMS's. (all slide settings are correct re submit on player, submit interaction trigger, incorrect and correct layer being used)

Testing in preview does not reveal the issue and it appears to have cropped up only once published and uploaded to an LMS.

We are wondering if the problem is that there are two consecutive drag and drop activities and this is disturbing the second submit button, as in both instances it is the second activity where the submit button will not show. Interestingly, on revisiting the first one the submit button disappears from the player as well - even though it was there for the first running!

Has anyone experienced this before? Is there are solution or known issue where it is recommended not to put two drag and drops after one another?