I’ve been modelling some time in Roblox and never faced this problem before.
I’ve also tried to apply smoothing angle but the mesh gets worse.
This is before pressing Play or Test mode in Studio. (The correct way)
This is how it looks when pressed. (The wrinkles)
Thanks for the help 
It might have to do with differences in graphics level between edit and play mode.
I would suggest using a mesh part rather than a union, as it usually looks better for materials.
Unions are extremely unstable in roblox and is mostly broken. It depends on the size of the object.
I’d recommend you go to blender and remake it there and then import it to roblox studio.
My graphic levels are at max, also when test it in roblox player I get the same thing.
I’m a newbie to blender but I’ll try to see if this can be smoothed.
