There is an SVN repository (single repository) http://example.net/svn

The repository contains several projects (directories):

http://example.net/svn/Project1
http://example.net/svn/Project2

User has full access to Project1 directory and has no access neither to root nor to Project2.

Everything works fine for a while: user checks out http://example.net/svn/Project1, commits and updates it successfully.

But sometimes trying to update leads to the following error:

Command: Update
Error: Server sent unexpected return value (403 Forbidden) in response to OPTIONS
Error: request for 'http://example.net/svn'
Finished!

Why does TortoiseSVN request something in the root???

I have noticed that this happens after somebody else committed copy or move operation. Checking out http://example.net/svn/Project1 helps till next time...

The main question: How to set up access rights for user to avoid these errors? Note, it's not an option to grant user any read or write access right on the root directory for security reasons.