Captivate 2019 - quiz slide accepts only one incorrect try - infinite attempts

Hi all - so I have a quiz slide using Captivate 2019s built in multiple choice. The master slide contains Back Submit and Skip and each have been stylistically edited in the Object Style Manager. 

We have a few multi choice, T/F and multi answer Knowledge Check slides.  Settings for the Multi choice/Multiple answer are:

Graded
Shuffle Answers
Multiple Answers (when required)
Points: 10
Numbering: None
Captions: Correct, Incomplete
Buttons: Back, Skip
Actions - Success Go to next slide
Infinite Attempts: yes
Retry Message: no
Failure Messages: 1

We are finding in testing, which I've not come across before, that if we get a question wrong (Incorrect message, please try again), that if we get the answer wrong again, Submit when clicked does nothing. So even with Infinite Attempts we can only get it wrong once. Is this expected behaviour?

Quiz Settings: Required - Optional
Allow Backwards movement
Under Pass - Fail - Pass Fail option is set to 80% (but these are just knowledge checks)
If Passing Grade: Continue
If Failing Grade - Allow User 1 Attempts <-- is this it?

thank you for any pointers