Invisible Light Source

I'm having problems with invisible light sources, as my players have noticed.   And as you see in the image, in neither the map, dynamic lighting, token or DJ layer a possible light source is shown. And more weirdly the players see that corner although their characters are not around and they are in the other part of the map. So my only explanation is that has to do with permanent or explorable darkness, but the Explorer's Mode is not activated, and putting a rectangle of permanent darkness is not a solution since I would have to remove manually when they come to that place. It may be that a token shared with everyone is showing its vision to the players but also I cannot find it. Please, help. 

It is possible to reveal an area as Explorered in UDL. You can remove an area as Explored by using the Hide/Reveal tool. Hover over the tool, choose Explorable Darkness, then choose Hide, then choose the method you want to use to select the area (Rectangle or Polygon). However, if the characters can see tokens in that area, then something else is going on. You can use the Select tool to try to select tokens in that area to see if there is one that you can't see. Try that on the different layers.

tokens in the DL layer can have lightsources set to it, I found this out the hardway a while back when they broke an api script that did just this.  Did you check the DL layer for a stray torch that is in the wrong layer?

I have searched all the layers and the only real explanation is that a token got lost when I changed the size of the map. The token can be so tiny that I can't find it–even when using the select tool. The solution I have found is not pretty but works:

el_herrero said: I have searched all the layers and the only real explanation is that a token got lost when I changed the size of the map. The token can be so tiny that I can't find it–even when using the select tool. The solution I have found is not pretty but works: Honestly, the solution is probably to use LDL.  The bug is likely just one of the many UDL glitches.  But switching versions can disrupt explored darkness immensely.  In LDL its called AFOW and currently AFOW is not resettable cause they broke the floating toolbar in many ways over the last month one of them being the reset fog button no longer working.