The contents of that training has changed.

Hi Guys. Sometimes when I start to > button to resume the training appears this message: "The contents of that training has changed. If you start again that training, your previous achievements for it will be deleted. Do you want to continue?" Obviously I never modified/changed the content of the training. Clicking ok, the course restart from scratch but the message above appears randomly other times. It's not a real problem but before "resetting and restarting" the course the button "Continue training" (in catalogue section) becomes unresponsive(no action on click). Any tips/support? Best regards