After the unnecessary patch that was released today which broke the game and didnt fix anything, Lavamancer's Fissure of Embermount stops working damage wise after about 10 or so seconds and doesn't start again until you replace it only to dissapear again after 10 seconds. You can tell when it breaks because the molten rock texture under the fissure dissapears indicating that the tower has stopped working damage wise. The molten power still works just no damage.
It was very painful to attempt chaos V just to see all my defenses disapear during the wave
Also, upgrading fissures will not help it either. :-(