I will upload the file tomorrow. There are few issues actually.
Data Smith doesn’t import multiple instances no matter what. Tried few copies of default blender monkeys (through collection instance in blender) - this works flawlessly in 5.0 versions as datasmith imports in 5.1 only 1 instance is imported and then bunch of empty actors in place of other instances.
Another issue that I noticed even in 5.0 is on a file I got from MEP engineer a converted cad file from Revit he gave me I imported to rhino(as I don’t have Revit) and then imported to blender to clean up etc and then exported to .glb 
I noticed that some objects are very slightly shifted - only in unreal(tried octane render and everything is in place) Like pipes don’t line up with fittings and coupling etc… Strange small position error I attribute to scale difference(maybe, although the more I think about it it doesn’t make sense why a pipe would move like 2cm)