I’ve attached a simplified file demonstrating the issue with a simple sphere fading from 100% visibility to 0% over 90 frames. If the sphere’s material reflectance channel is switched off, the sphere disappears from view as intended (at frame 85 it is virtually invisible). With the reflectance channel on, though, a white reflection (of the sky object, I think) remains visible at the same intensity throughout the animation, and just the base color of the object fades. At frame 85, the sphere appears a fairly intense white.
Thanks for looking!