Converting to Storyline 2, player bug.

We are planning to upgrade a suite of courses from SL1 to SL2.

On each question screen, we have the slide set to "Resume saved state" (i.e. when you go back to that slide, the question shows in its answered format with feedback).  

The question slide has Next and Prev switched off in slide properties. In fact they are switched off on all screens as we are using custom master slides with navigation. 

After converting from SL1 to SL2, when you complete a question screen and go on to next slide, if you then select Previous, the question screen reappears with the standard player Next and Back buttons showing. See screen grab.

This bug only happens in the HTML5 version.

 It is affecting a lot of slides on a lot of our courses. Has anyone else come across this problem? 

Thanks

Peter