"Sync" sometimes does not delete folders

Hello,

Sometimes I get a wrong result when using the task "sync".

I try to synchronize a directory which is defined as a share on a 
windows system (source) to a local directory (target), i.e. the local 
dir should look like the share after the sync.

But sometimes, after the sync, I see that dirs which do not exist on the 
share are not deleted on the local file system. Instead, just the files 
in the dirs are deleted.

I still have not been able to track down when exactly it happens. 
Sometimes it works as it should (i.e. the dir is deleted), but sometimes 
it does not.

Has someone experienced this? What was the reason and the solution?

Thank you!
AL