Explorer Mode Artifacts?

Posting this here in case its a common issue with a known fix. Everything I search for brings up issues that do not appear to be related to what I am seeing. I recently got to start using dynamic lighting again. My player with the PC that couldn't handle it got an upgrade. I'm not sure what is relevant here: I'm running dynamic lighting, explorer mode, and update on drop. No API scripts are in use. All of the walls on this map were drawn with the polygon tool. I get the same results in both Chrome and Firefox. I've tried it on a few copies of this map, using new images and new walls on a new canvas each time. The artifacts clear when a token with light or dark-vision moves through the area. Randomly, later, a portion of the explored area reverts to this.

Hi Hildy! I have never seen anything quite like that. Very odd indeed. The first thing I'd check is to ensure that the map image itself is not giving off light or have vision. Does the behavior occur when running in a private browsing (incognito) window?

The map having vision didn't occur to me. It does not, but interesting idea. I have not tried incognito. What I can say for sure is that – although I did see it in Firefox once – it does not seem to be coming back in Firefox the way it does in Chrome. I'll continue troubleshooting but for game night, I'll just switch to Firefox for now.

Vision is not usually an issue, since it is on the map layer, where vision is non-functional. But many people have had issues that arise from a map image casting light unintentionally. It was a shot in the dark. no shame