Issue on use of reflection dim distance fallof

[gildas_baron]

Hello,
I've got an irregular issue on the setup of the dim distance for reflection.
The problem is like a bug on the falloff.
Sometimes it works and it's pretty cool but sometimes even if the fall off is set to 1.0, it's like 0.0. No soft transition.

Someone encounters this problem?

Thks for any help

Max 22 + Vray 5 2.2

[hermit.crab]

It's not happening on a fresh scene. Could you simplify and attach yours here? Screencaps would be lovely.