This bug exists for a long time now I think (Occured in 1.071) I dont know what causes it,I took a pic of it so you guys might figure it out. After tanks fire with their cannons,sometimes the "flame" doesnt disappear and keeps making the "fire-noise".
I've seen that in loads of mods, even HL2:DM. I think it happens when you hit something very close to you. Not sure that it can be fixed