We setup sharepoint 2016 trial. The enterprise search center works as expected - for anyone. The search box of the project site however, does return results only for some users. So the same documents are not found, only for some users.
There is no logical explanation to me. All users are allowed to view these documents, so search should find them as well. This effect is not seen on another sharepoint test machine that the same people have setup.
We searched the net and found people with this problem who claimed, their solution was to change permissions on that problem user's AD object, which we tested, but no success.