checkpoint question freezing / unresponsive

I'm new admin of an LMS that had some content created with Articulate Studio'13 I belive....

Currently users are reporting random unresponsiveness in our workshops when they hit a checkpoint question in a presentation.

I am able to reproduce this in a couple different courses if I quickly hit submit before answering the question.

Other various issues reported (that I can't reproduce) are text not displaying on slides and unable to click on a checkpoint / question answer.

Note: these issues don't seem to be slide specific. 

See attached of an example where I have clicked submit before answering a question.  The question disapears and then re-clicking sumbit just says I must first answer the question.

Any guideance is appreciated  -

Thx, 
Josh