I basically run the following command to initialize and start fetching:
git-svn clone -s --repack=500 -rBASE:HEAD svn://anonsvn.kde.org/home/kde/ ~/repository/GIT/KDE.git
(yes -rBASE:HEAD is redundant, so I doubt that it influences anything.)

Sometimes, due to my internet going down, or I have to shutdown the machine, the fetching gets interrupted, so I just resume with
cd ~/repository/GIT/KDE.git
git-svn fetch --repack=500

Usually it starts to fetch again, sometimes it notices an index mismatch, seems to correct it and fetches on, finally, git-svn can't seem to correct the mismatch, and fails.

I've tried deleting all .rev_db* files, and all index files in the .git/svn/*/ directories, git-svn rebuilds them, but fails with the same index/checksum mismatch.

KDE.git/.git/config :
-----
[core]
        repositoryformatversion = 0
        filemode = true
        bare = false
        logallrefupdates = true
[svn-remote "svn"]
        url = svn://anonsvn.kde.org/home/kde
        fetch = trunk:refs/remotes/trunk
        branches = branches/*:refs/remotes/*
        tags = tags/*:refs/remotes/tags/*
-----