The function is there in Teams - in the Files Tab. Steps to reproduce:
You just get an error saying "Sorry we ran into a problem" the file was not copied.
The work around is to Open the file in SharePoint and copy from there.
All this is because we are unable to share a file from a Team with anyone outside the organisation! So frustrating!!
We've just started with office365, but we run into the same problem als described here almost a year ago
has someone found the reason for this 'file lock'