fog of war issue

the fog of war disappeared in the middle of a dungeon i was playing in today. i had to reload to get rid of it.  p.s we are a little farther up on this one but this is what i saw when i switched back to the tab

Hello ilikestuff, I'm sorry to hear that you're having issues with the Fog of War. To rule out potential issues, please carefully work through these steps of our guide to  Solving Technical Issues : Step 1: Make sure to use the right browser Please check if these issues persist when using both Chrome  and  Firefox. Step 2: Ensure that there are no extensions/addons interfering with Roll20 Please disable  all  add-ons/extensions. Step 3: Clear your cache If none of the above succeeds, please thoroughly work through all of  Step 4 .  (Don't forget the complete Console Log!) Thank you!

I'm not really sure how i would check if any of that would work without someone setting up a map for me to mess around on. reloading the page fixed the issue but another friend said they had the same issue that same session. its not an issue i can't get rid of its just some odd bug. it happened after we took an about 45min break from the game do to un related things. when we came back we both had the issue.