Petrified ember event started on its own

When I approached a petrified ember encounter, it already had its special monsters around the tree and hitting it. It didn't have the UI of an ongoing encounter (the tree's HP bar). After I killed the monsters, the encounter completed and the usual lanterns(?) appeared around it, though there was no portal with a miner (but I'm not sure if they normally appear every time). The minimap icon was visible before I approached, but it was gone after I killed the monsters; I think it disappeared when the event counted as completed.

Potentially notable is that there was a Blight encounter in the same map and not far away (a screen and a half away, I think), and I completed it before I approached the ember but after I came close enough that the ember's icon appeared on the minimap. Since they share some assets, I wouldn't be surprised if there was an erroneous shared trigger too.

Report reference number: 3 676 659 953