Experiencing this in my studio as well since 3 or so days ago. It somewhat makes my cab look overly metallic after the union (the initial blue and the cab union shows a considerable contrast in comparison)
And then changing the smoothing angle does this as if it’s trying to fight with the shading
The decal issue for me shows up on both sides as noted by Dan but leaves only one face internally without the decal
Even unioning simple objects causes weird shading issues. (yes, I enabled “Use part color”)
It seems Roblox is refusing to respond to this issue after forcing CSGv3 onto everyone. How sad.
(Image courtesy of user “hurtfuleagle2”)
@subcritical could this be a result of the new part shape/size changes? This problem seems to have started around the same time it was released.
We’ve file a ticket to your internal database, and will start investigating!
Thanks for the report!
I tried it and it didnt fix it for me 
Any updates on this bug? It seems major enough to be high priority in my perspective.
Also, why does it say that this topic has been solved? It definitely has not been solved as the bug is not fixed yet.
It’s because the OP marked it as solved and an automatic lock timer has turned on!
Please don’t mark a reply as solved if that’s not the case, as it’s messing our internal process as well!
We don’t have updates yet, but we may have some this week! Thank you for your patience!
Here’s another example of this bug where the color on the union is different even with UsePartColor enabled
After checking to replicate the bug today, it appears that it already has been fixed. Even un-unioning bugged unions appears to fix the issue.
More views of it seeming to be fixed! Great news!
Only slight issue is that unions are not fixed automatically and you must separate/redo them for the shadow issue to be fixed.
Either fix is not fully rolled out yet or the issue is still occurring:
https://cdn.discordapp.com/attachments/947255567393632276/1128733935812218950/Random_-_Roblox_Studio_2023-07-12_13-04-23.mp4
I am still having the problems as listed in one of my devforum posts, sadly I cannot post bug-reports, so I will link it here. Please revert this update so developers CAN use CSG v2 without being forced to V3 and having bricked engines.
I’ve had this exact same issue! Negating parts just makes them dark and there is no real way to fix it.
I believe this is fixed by now? Can anyone deny this?
This has been fixed. It can be marked as resolved now.
I can deny this, still having problems with unions.
