Incorrect Material Assignement to groups

Hello,
I have a very strange problem with some object getting assigned random material after reopening a file, and I am not sure where does it come from.
The file it is fairly big, but not out of the ordinary and it didnt give problems until a week ago.
It happens mostly with grouped objects and blocks, just some of the grouped objects gets assigned random materials.
I dont know if this has to do with the latest version of rhino Version 6 SR7 (6.7.18210.11281, 07/29/2018 ) or something else.
I also suspect that it could be related to the use of Snapshots, which I just started (never did before)
This file also use quite a lot of visualarq objects, but because the problem happens mostly with groups of non-parametric objects I tend to exclude it
It is quite annoying and time consuming to fix it, because one never knows if the problem will appear or not…

Hello,

Is there anything in common between the objects (or materials) which are involved in this behavior?
Do you remember when it first occurred?
Could you please make a copy of your project, clear all snapshots data and see if the problem is still reproducible?
We can take a look if you are willing to share the project (either send me a PM or email at support@chaosgroup.com)

Kind regards,
Peter