SVN connection problem with "svn: mergeinfo" property

I have one big merge problem - it starts with a strange message: "The server sent an unexpected return value (401 Authorization required) in response to a PROPFIND request for '/svn/autogroup_projects/.../Data.sln'".

Indeed, the folder does not exist in the branch, but we used it in trunc (it was modified separately). And this file is only one with the "svn: mergeinfo" property, and the value is empty. And of course I have access to SVN-401, the error code is very strange to me.