I followed this tutorial in order to make a muzzle flash for a gun.
The muzzle flash sticks to the barrel of the gun, and goes back and forth from emission to transparent.
In my blender file. When the mix shader is 1, the transparent texture is active. When the mix shader is 0, the emission shader is active.
I though you were using Eevee . My bad
I’m wondering what could cause that kind of shadow to appear. It may sound stupid at this point but have you check already if transparent shader color is pure white?
Other way to solve the issue that comes across my mind could be to uncheck diffuse visibility in object tab. That would make the emission shader visible but cycles won’t render shadows for the object itself