You guys are making a wonderful tool, thanks for all the hard work! Was excited to get a chance to use it for the first time today.
To start with I created my maps walls using the tiles as drawings so they did not snap to the grid. I'm not sure if this is what caused the issue.
When lifting the fog of war for my players they couldn't see the walls. To get it to show I had to go into the map layer with the select drawing tool and move each piece to get it to become visible. This would be wonderful to get fixed if possible.