Whole map revealing for players

Hi folks, having a wee issue with lighting on roll20. Some of my players if they accidentally move outside a wall reveal the whole map to themselves. It also lights up the whole map on my end. This is happening to multiple of my players and on multiple maps in different campaigns. Any ideas how to stop it? I was wondering if it was roll20 struggling with the size of the maps (DoMM size). Thanks in advance for any help! (Explorer mode is on and players are using darkvision, there are no light sources)

Hi David! Here are a couple of things to try: 1) turn on "Dynamic Lighting Barriers Restrict Movement" on the Page Details tab of the Page Settings for the map they are on. That should keep them contained in the area they are exploring. 2) Make sure you have turned off Sight on any NPCs. That should be the default for the module, but it's possible it got changed. That can cause the lighting up effect if a lot of darkvisioned characters are gathered together. 3) In some cases it can be helpful to make yourself a specified additional controller on each PC. 4) To test any of these adjustments, you can use a  Dummy Account  in between games.

Oh, and as a note, yeah, DotMM is probably the largest and most difficult map to run of Roll20's WotC offerings. Print module writers don't design with VTTs in mind, unfortunately. One more tip: If you are using Explorer mode, make sure everyone has Hardware Acceleration turned on in their browser. It makes a huge performance difference.

There is a patreon content creator that offers free DotMM maps broken into quadrants that perform very well in roll20.  I dunno if its against the rules to post competitors to the marketplace as hes not offering stuff there.  His work is absolutely amazing and I went with his Dragonheist stuff AND his dungeon of mad mage stuff.   As for dynamic lighting walls shutting off.  I don't use UDL, but in LDL I don't have any issues at all.  Infact with the latest patch I'm even able to run the party with AFOW and LDL running at the same time in Dungeon of the Mad Mage.  I dunno what they did but they accidentally made LDL awesome ;)

FWIW, openly posting offsite sales is against the CoC, but nothing prevents you from sending the link in a PM.

Thank you for your help guys, have tried the things you suggested and completely fixed things for one of my players. We have determined the others PC is just not handling DL at all. 

I have never had an issue with LDL failing to work for a user.  My thoughts would be that you haven't changed over the tokens lighting settings to legacy dynamic lighting properly if you are trying that.  When you switch to legacy, sadly they did not make it simple, which is partially the biggest reasons why I cannot stand UDL, they should have made it universal, a simple switch between the two.  Then they would have had a far cleaner test bed for bugs, instead its a gigantic project for every DM to have to swap between them when their players machines fail in UDL.  First you change the page setting, then you have to go in and change each token and default tokens LDL section as well, make sure has sight is selected.  Additionally, afaik the api keys for UDL and LDL are not backwards compatible with each other so if you use api to control visions and lights you also need a whole new set of macros(another annoying poor design choice).