Unwanted shadows on texts in bubbles after editing

Hello everyone, 

I have a frequent problem with unwanted shadows hen using storyline for recording. When I have edited the recording and save it everything is fine but I find that sometimes when I open an already edited e-learning that there are suddenly shadows behind the text in the bubbles on a lot of pages which I have not set at all. The only way to get rid of them is to edit the texts in the bubbles all over again. It does not work to use the buttons which are available to set the shadows intentionally. I asked my colleagues here if they had similar expierences but none of them had and nobody had an idea where this comes from. 

I have attached a screenshot to show how it looks like.

It is very tedious to edit all those texts again and I do hope there is an easier solution to this problem. 

I would be interested to hear if anybody in the community has encountered  this problem as well. 

Best regards

Agnes