Player sees too much

Hi there I've got an issue in my game at present where one of my players can see the whole map.  I started the game out with Dynamic Lighting and Explorer Mode turned on, which seemed to work fine when I was doing pre-game testing, and indeed works fine for the other players.  But one of them can see the entire map, including the bits that nobody has been to yet.  I've tried turning Dynamic Lighting and Explorer Mode off one at a time and although the other players see the changes as expected the one-who-sees-to-much still sees, well, too much. The players were all invited at the same time and in the same way. The characters were all created at the same time. I don't know if this is relevant or not but the affected player is running Roll20 in Chrome on an old laptop running Windows 7 Does anyone have any ideas what might be causing this, and how I might resolve it? Many thanks

Updated dynamic lighting has massive amounts of bugs and conflicts with very common extensions that random people on the internet innocently run for other things like ad blockers.  My suggestion to you is to log a complaint with customer service that they have hidden legacy dynamic lighting all the way at the bottom of every dynamic lighting page, and ask them to move it back to its own tab and implore them to continue supporting it as it is the only dynamic lighting that works on their platform reliably over the internet.  Personally, UDL is a giant mistake and all the feature does is boost the profit margins of Foundry and Fantasy Grounds.   TLDR:  Switch to LDL, use Advanced Fog of War with LDL enabled which is at the very bottom of the token and page dynamic lighting pages and they have to be set in both places for it to be on properly.