Permissions lost when changing from public to private

[escupham]

We've found that when changing an O365 Group from public to private in the document library interface, the permissions on that document library are lost.  Even though say 10 people are members of that group, when we switched it from public to private those 10 people couldn't access the document library, we had to reassign them edit/view permissions on the site.  Is that expected behavior?

[#2]

To my knowledge this is totally unexpected...just to clarify: you don't have custom permissions in the document library, do you?

[#3]

Thanks, no custom permissions.