SL360: Random text is missing when overlaid on top of video in IE

I'm hoping someone can help me find a solution to a very random issue I'm experiencing with one of our courses: When viewing the course in Internet Explorer, some text boxes are randomly missing chunks of text- it almost looks like there is a box covering the letters. However, if I resize the browser window, the text magically reappears... 

We are using the modern player and the client's font is Museo Sans. I did find this older thread (https://community.articulate.com/discussions/articulate-storyline/text-missing-in-storyline-360) and tried their recommendations- toggled the modern text feature, turned it off completely, stopped the video before the end of the timeline- but nothing worked. The end of the thread says this issue was fixed in a 360 update for Chrome, but the client needs it working in IE as well. 

I really can't find any rhyme or reason as to why only a handful of text boxes have this problem- others that also appear over video look just fine. Any ideas on how to fix this are much appreciated!