Instance range - keeps changing on it's own

[sbstnc]

Hi,

4.01 and 4.02 same thing is happening. Not sure if it happened prior to that.
Instance range is being used to control a mix texture.

Randomly, when I open the scene sometimes, colours/textures are different. No change to objects (they are in an Xref and do not change or animate, static models) and no change to Instance Range node.
I notice this most between Mac, PC, and farm. Sometimes they give the same result, other times unlucky and they do not.

Not sure if a bug. If models don't change why would the mix be affected?