V-Ray Material is lost

[flat]

There is a report from my customer that opening rhino files at a later date will cause all V-Ray materials to be lost.

Since the problem data contains NDA, I sent it to support@chaosgroup.com.
ticket number is: 413-626-017

What is the cause?
Is there a way to recover the material?

Using V-Ray 3.60.03 + Rhino 5 and 6
do not use the scene of V-Ray 2.0 for Rhino

[palosanto]

I had this problem a number of times but exiting Rhino and rebooting has restored the materials normally.
Also, exporting objects with materials that were originally created in Rhino 2, causes these materials to get lost when opening the exported file. This is a known bug.

[flat]

Material information is completely lost in the problematic Rhino data. Probably can not be restored.

We receive mail from Chaos Group support and are looking for a reproduction method.

I will report if there is progress.